The project is for my niece. Framing a piece of 4'x6' 3/4" plywood to be a kind of mini stage -- but the plywood is a bit warped. I figure I'll cut a channel into these and frame the plywood with them, forcing the plywood to seat flat in the channel.

Or maybe I'm over-thinking it. I tend to avoid screws in my construction now, but I could just build an under frame for it and screw it down. Hmmm.

The channel approach has the added benefit of concealing and protecting the plywood edges. It'll certainly look better that way.

Still leaning towards channel.