Use bathroom caulking to hold the carpet to the floor!
I flipped the carpet over, and swept underneath (ew!) I laid the carpet and then I got out the caulking.
I spread a thin line all around the edges and a few thru the middle.
I put extra in the corners, just cause I wanted to make sure it stayed down. I waited about 3 minutes. Enough for the caulking to get tacky, but not dry. Then I flipped the carpet over, positioned it where I wanted and stepped on the edges of the carpet to tap it all down.
The carpet was so big I didn't get it straight where I wanted it at first so I had to move it a bit. Some caulking got in places I didn't want it, but a wet rag cleaned it up real easy.
That's what works for me!