Gather your play mat materials. Find a carpet seller near you either by going to a home product or national carpet seller's ad online and searching for one in your area from their site, or from your local Yellow Pages. If seeking natural play mat materials only, refine your search to carpet outlets that specialize in those materials. Contact the stores and ask if they have small rug remnants or samples available. In some cases, they may give them to you for free, in other cases, they may charge a few cents each. Keep searching until you find a carpet dealer who has what you're looking for. You may find all the carpet remnants you need already at the right size. If you need to trim sample edges or cut to size for your play mat, use carpet shears, which you may be able to rent at a home supply store or tool store if you or your friends don't have one.
Lay out the play mat design. Set the remnants or samples out, face down, in the design you choose, then measure the total length of the areas that need to be joined together.
Get the materials for your play mat seams. With the above measurement, go to a home product store and get the right amount of carpet seaming tape. Though it isn't the cheapest tape you'll ever buy, you won't need much for this play mat project.
Finish the play mat. Attach it to the seams by pressing the carpet onto it. It sticks very well and even professionals use it. It works nicely when your play mat (or play mats) are set onto floors.