How would I temporarily adhere heavy plywood to back slash area?

Any pliable adhesive would not carry the weight. Should have just adhered the faux rock directly to the wall. In your situation you can use toggle bolts in the corners to attach it to the wall.

https://www.homedepot.com/p/Everbilt-1-4-in-x-3-in-Zinc-Plated-Toggle-Bolt-with-Round-Head-Phillips-Drive-Screw-10-Piece-803932/204273383?mtc=Shopping-B-F_D25H-G-D25H-25_3_FASTENERS-NA-NA-Feed-LIA-NA-NA-Fasteners_LIA&cm_mmc=Shopping-B-F_D25H-G-D25H-25_3_FASTENERS-NA-NA-Feed-LIA-NA-NA-Fasteners_LIA-71700000065880652-58700005819508955-92700053176328159&gclid=EAIaIQobChMIqayHh5jT6QIVBdvACh068QBiEAQYASABEgJLM_D_BwE&gclsrc=aw.ds

How to attach toggle bolts

https://www.youtube.com/watch?v=dMaWRaJ2GXQ

I had a very heavy tile decorative piece I used above my range in a rental property. Did not want to permanently affix it to the wall. I used 6 pieces of velcro and it did the trick. :)

The best thing to do is to screw it into the studs in many places. You won’t find a strong adhesive that will hold that weight well but still let go tidily.

Command strips might do the job.

Janet: use an inexpensive stud finder --- I find this one is not fancy and works just fine

https://www.amazon.com/gp/product/B000IKK0OI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

thanks Nan🤔

Hi Janet, Check out this link to some great construction adhesive products. https://can.sika.com/content/canada/main/en/solutions_products/home-improvement/02a024/02a024sa008.html

I agree with finding the studs and screwing it into the studs.

Use liquid nails

why will you like to do it temporarily ?

to remove the faux treatment and perhaps redecorate with another theme

Use a stud finder and attach it with stainless steel screws.

If you plan to use screws, locate the studs in the wall and screw the backsplash into them. It'll stay just fine. Any kind of adhesive will wreak havoc on your walls when you go to remove it.

thank you. I am expecting a stud finder from Amazon any day.

thanks to all the Hometalkers that helped me find a way to attach my faux rock backsplash. Can you tell I love green? You can't tell from the photo that it is immensely textured as well. The ochre areas are where the screws are attaching it to the wall so that when I get tired of it I can take it down and do some other kind of backsplash!