Here's the second of the little 8 inches x 6 inches plyboards, I am aiming to decorate. Trying to think of ideas, trying not to use glue, but I have to confess I did with this one. After varnishing I wrapped thin wire around the board, three verticals and three horizontals. I didn't measure the distances apart, just guessed. This made a grid, then I secured the wire to the board at the junctions where they crossed.
I used Hi Tack School Glue. It comes in a small plastic bottle with a narrow nozzle, to put the glue exactly where you want it. It's a bit like PVA glue. Spread it on both surfaces and press down. Work from the centre easing out the air bubbles around the edge. Wipe excess glue off with my fingers.