To seam the placemats together, use single sided carpet tape. This is the carpet seam tape I recommend.
Remove backing from tape, and place the mat halfway onto the tape, saving the other half for the next mat.
Join next placemat to the first, pressing down on the seam to secure.
Repeat step with another placemat. The placemats making the circumference edge of the rug will be joined on 3 sides to other mats. The center mats will be joined on all 4 sides.
Press the seams together to create a tight fit.
Continue steps until custom placemat rug is completed.