I have an old pic around somewhere, but my planer sled is a 3/4" plywood piece - about 6' long - with a straight 2x4 on edge on both L and R sides. 12" planer so max width of the sled is somewhat less than 12" and max board with is likely 7-8".
I just adjusted the height of several drywall screws to fully support the twisted piece, then took light cuts on the planer. Establishing one flat face that way I could plane the other side flat too. Worked when I needed it - but it ain't pretty, just utilitarian.
EDIT - shows how good my memory is... there is no plywood in this, just two 2x4 on edge with blocking in between. Shown here. Piece being planed is shown on edge in the pic, but the wide faces (of the 8/4 piece 6" wide) were the ones being planed. Planer has at least a 6" depth capacity.