Pity people waste time with clearing boards. All that is necessary is to gently shake and brush the bees off each frame of 80% or so capped cells and stick them one by one into an adjacent empty BB or super, putting a lid on top to stop bees descending on the frames that you have just cleared. The odd bee or two will get in or fail to be removed but that is soon dealt with when you move the box(es) into your bottling shed/room - ie just open the window and they will buzz off. Amazingly simple really. I made Canadian clearing board some years ago but apart from first time don't bother now.