You can get foam glue at your local fabric or craft store. If you use regular glue, it may melt the foam. I've glued foam together with foam glue and it held very well.

Good luck with your project.

There are spray adhesives made for bonding foam, and that is what you should use.

BUT - memory foam should NOT be used for cushions. Do you really want butt prints on your cushions?? Aside from anything else it's incredibly expensive for this use. Are you sure what you have is memory foam?

Use a high resiliency foam. Call your local upholstery supply store - many of them will custom cut your foam for very little cost.

And the stuff they sell at most craft stores - Nu-foam and such will collapse after about a year's use. Don't bother.

Thanks for your comments, Mary. I don't know if it it is actually memory foam. My DIL gave me this piece of foam all rolled up and when unrolled expanded into a 3" slab so I thought it was memory foam. She doesn't live near me so I couldn't be with her when she bought it. On her last visit she brought it here. It is for a window seat in my granddaughter's room and as her dad says, it will probably be piled with stuff all the time.
Since this is what I have , I guess I'll just have to work with it, but thanks for your advice re: adhesives.
Carolyn

I know you've decided to use it anyway, but here's a test.

Unroll the foam, and press down hard with your opened hand. Wait a few moments. Remove your hand, and if it takes a few moments for the hand print to disappear, it's memory foam.

If there is no imprint at all, it is probably cushion foam, and much better for your application.

Regular foam is easy. I have used Duro spray adhesive with great success. follow the directions (spray both surfaces, wait 60 seconds, press together) Do this outside, or there will be surfaces inside your workroom that will be permanently tacky. I don't know if memory foam will react differently to glue.

Whatever you do,DO NOT use that Nu Foam.I did once and mine didn't even last 6 mos,and i'm the only who sat on the chair.
Kathi

You didn't say how long your cushion needs to be but, the longer the cushion the more likely the ends of the cushion will pop up when someone sits on it. You might want to test this before making a cover for one long cushion and consider making two shorter ones. Just a thought.