Diorama guys help needed. Clay won’t stick to base.

[ScottsGT]

My first effort at this.  Plywood base, raw and no finish.  I picked up a couple of the small buckets of crayola modeling clay at Hobby Lobby.  Did a test spot last night where I rolled out a small piece and pressed it into the wood and let it dry.  I was hoping it would stick.  Even wet one small part under the clay with saliva just to see if it let the clay soak in. 
This morning the entire piece popped right off with no effort other than touching it. 
Should I try brushing on some wood glue like tote-bond or Elmer’s white glue before flattening out my clay on the base? How about Mod Podge? 

[ScottsGT]

Just a follow up, watch some YouTube videos.  Apparently the trick is to soak the wood surface pretty good with water and then work in the clay.  Running a test spot now to see how it works. 

[CANicoll]

I know you said its plywood, but no need to varnish it to keep it from warping? 

[ScottsGT]

38 minutes ago, CANicoll said:

I know you said its plywood, but no need to varnish it to keep it from warping? 

1/2 ply with 3” doubled up on the edges for a total of 1” thick. I don’t think a wet top is going to warp it.  Now if I threw it in the hot tub to get it really wet, we might have a problem.  
Besides, if you varnish it, the clay won’t have anything to bite into.  Supposedly it’s the swollen wet wood fibers that bonds the two.

And I’m working short sections at a time.  Right now it’s just testing. I’ve got to run get some molding for the edges and trim it out so I can proceed. 

[CANicoll]

Ahh, gotcha.  What about rough sanding (60 grit paper) the plywood to really roughen up the surface?  I thought masking the Cat canopy was a lot of work!!

And/or put down some staples or screws - not fully flush with the board?  Gives the clay something to grab onto?

[ScottsGT]

Just an update…wetting the wood did the trick.  It would take a chisel to get that stuff off the wood now.  I did get some drying cracks, but I can go back and fill those in.  

[Maker666]

You should place some pva glue in between both, and let it dry, they should stick