Cement stuck to frame boards

I setup some 1x4 frames for a cement project. the entire area was framed in, then within the main section, it was subdivided with additional frames.

It's now a day after pouring the cement, I've removed the outer frames and a few of the inner frames, but some of them are stuck. I could apply a lot of pressure to remove them, but on top of that concrete (and butted up against the frames), I put some fairly delicate slate. So, using force would remove the boards, but really damagae the slate, as the edges would lift up.
I did put some non-stick cooking spray on some boards, but ran out of it mid project, so not all boards were pre-greased.

Any suggestions for helping to ease out the remaining stubborn boards?

Thanks!

Actually, that might work. Moisten the whole thing but try and keep the wood particularly moist. You should be able to loosen the wood fibers to the point that it'll pull apart.

I have a couple of vehicles that take 5 gal/oil change so we always have plenty.

I'm also unaware of your "rope wick method". Please?

T_Bone