I sandwich on a bar type island thing in my kitchen. I use clamps to hold the backing down...using masking tape to hold it until my clamps are all "installed." The clamps are from Harbor Fright and are designed for lumber, I think. (My 'surface is about an inch thick.) My sister bought a ping pong table just for this use, and she uses clamps like those used to hold lots of paper together.
I would want to protect my dining room table somehow, if I used that. I wouldn't want to scratch the top with a pin.
I do have to pin in three different stages....first I do the middle and then I go to each side. I just move the clamps after I am through pinning the area that is on the surface. It works pretty good, though my sister's ping pong table works better.
I hope you figure something out. Pinning on the floor is no fun!
Dina