Here’s what I’d do in Rhino 3D. I’d draw my piece of wood as a rectangle and extrude it up into a solid.
I would draw my arc in the front view as a surface and extrude it along the length of the block.
I would split both parts by each other and delete the waste. Then I’d add the curve to the remaining block as an enclosed solid.
Without drawing, you could do a middle pass .25 deep along the length, then change the X and Z over and up on each side of that in increments. Keep doing that until you roughed out the concave part.
You may be able to play with the gradient app like path warp and get something similar,
or add the shapes together and create the shape you want, but those are things I am not familiar with.
This is a 4 x 7 in easel. I don’t have pro or I’d save it for you to use.
