These are the supplies I used:
ATG double backed tape, dry iron, 3M Super 77 spray fixative, Tacky Glue, Artist’s tape, foamboard channel spacers, brown paper, mat knife, a mat of archival matboard that could have had over cut corners and it wouldn’t matter, linen fabric ironed absolutely smooth and cut a little larger than the mat. For the mat I could have used 1/8-inch Bainbridge Artcare Foamboard (the only brand that says it is archival, meaning better than acid-free). However, it’s more difficult to wrap a thicker mat, so until someone has enough experience to know just how deep to make the diagonal cuts into the corners, it’s easier to show the matboard mat. It won’t have much, if any, bevel showing, but it makes a nice, sharp edge.
Take the mat outside and lay it on a large piece of cardboard on the grass away from anything you don’t want overspray to reach. Spray the adhesive about 10 to 12 inches from the wrong (not beveled) side surface of the matboard. (As mentioned before, there isn’t much bevel that shows once it’s wrapped, and the straight edge gives a better, sharper final edge to the linen wrap.) Begin spraying off the surface of the mat, and use a steady cross motion from one side to the other, always stopping the spray when off the mat surface. That way if there are any drips of fixative, they’ll be on the cardboard and not on the mat. This spray adhesive remains sticky for several minutes, so you don’t have to run inside to continue.
Return inside, and lay the sticky side of the mat up. Carefully place the fabric on top. You can move the fabric if needed, so long as you don’t pat it in place, until you’re satisfied with the way it looks. Try to get the weave of the linen as close to straight across the matboard as possible.
Set the iron on its cotton setting without any water. It’s important to use a dry iron for this step. Place heavy brown paper over the linen and mat. Don’t move the iron back and forth, but rather set it in one place for about four or five seconds, lift and place in the next position, and continue until the whole area has been slightly heated. If the matboard warps a little, turn it over and heat the backside—but always cover with brown paper first.
Use a sharp mat knife to cut the inside piece of linen from the mat. Place a ruler along the inside edge of the mat. That width is enough linen to leave for turning over.
After cutting away the inside of the linen, carefully cut diagonally into each corner. You want to cut almost to the corner, as the cut will show on the right side if you cut too far. You can always cut a little more later if needed. Illustrated below is what it will look like when you’re finished cutting out the inside of the linen.
Apply double backed tape right along the inside edge of the mat. This will hold the fabric in place, so go completely from one edge to the other to be sure to cover the whole area.
Cut a piece of clean matboard about 2 or 3 inches wide and 4 to 6 inches long. This "spatula" is used to help get a good, even turn to the linen. Place the spatula under the right side of the linen along the middle area of one edge, and firmly pull towards yourself, adhering it to the double-backed tape. If this is a larger mat, work from side to side after this initial turn until you come almost to the edges. Leave about 1 inch from each corner free from turning for now. Using this "tool" makes a smoother, cleaner edge than using your hands alone.
This is an image of the long side of the spatula.
Next, use a very thin tool to apply Tacky Glue to the inner corners. I use a broken piece of plastic broom "thatch," but a toothpick works well too. The Tacky Glue is a product used to keep fabrics from fraying and doesn’t yellow as other glues might. If needed, now is the time to make any adjustments to the cut into the corners. If the cut you first made won’t turn “square” into the corner, carefully cut it a bit deeper. This isn’t difficult when using the “wrong side” of the matboard. It’s a little more difficult if you choose to use the beveled side of the matboard, and sometimes very tricky if you’ve chosen to use foamboard as your mat. The deeper the bevel, the more difficult it is to get a nice, square corner. Stick the thin tool along the inside edges of the corners, and get just enough glue inside to hold the corners in place and not have the linen fray any more than it already has. Don’t get too much on the fabric so that it becomes sloppy wet with glue. Finish turning the last bit of the corners with the matboard spatula. Then run the spatula along all edges of the mat to be sure they’re smooth and tight.
Trim the extra linen from the edges of the mat. (I don’t bother finishing these edges as they’ll be covered with the frame edge and I’ve never had a problem with them fraying.) It’s easiest to do this now before the next step.
To attach the foamboard channel spacers, use the double-backed tape along each outer edge of the mat. Make two rows to be sure the channel spacers will stay in place. Cut the channel spacers about ¼- to ½-inch more narrow than the width of the mat. It needs to be wide enough that it’ll cover the edges of your artwork, which will be held firmly in place once framed. Align the outside edges of the mat and channel spacers, and firmly push them in place. If any channel spacer is longer than the edge of the mat, cut it off evenly so that it’ll fit well into the frame. Notice that the channel spacers cover the edges of the linen near the mat window so any fraying that might’ve taken place doesn’t show.
Mount your painting on another board of your choice, and place the mat on top. Put them both into the frame and finish the back appropriately with a dust cover and flat hangers with good framers’ wire.