The white foam in this picture does not have any contact cement on it, but if it did and I was going to stick a large piece of fabric to it I would cover the glued surface with 3/8" X 3/8" sticks as shown.
Next I could lay on the fabric and position it as I wished without worrying about the two pieces sticking together out of alignment. Of course you can cut the foam much larger than necessary, which is shown here, but that is only because I didn't have the proper sized piece of foam for the picture. Normally I would cut the foam only slightly larger than the object piece. Your mileage may vary.
This is an actual piece stuck to foam, the fabric is 76" x 15". I would not try to lay this thing out without the sticks. I have seen many people try, and yes most of the time they are successful, it is the one time you are not that makes you rethink the process.
Next I could lay on the fabric and position it as I wished without worrying about the two pieces sticking together out of alignment. Of course you can cut the foam much larger than necessary, which is shown here, but that is only because I didn't have the proper sized piece of foam for the picture. Normally I would cut the foam only slightly larger than the object piece. Your mileage may vary.
This is an actual piece stuck to foam, the fabric is 76" x 15". I would not try to lay this thing out without the sticks. I have seen many people try, and yes most of the time they are successful, it is the one time you are not that makes you rethink the process.