A neat way to (sometimes) get the most efficient use of stock w/ knots and defects is to take a photo of it (if need be, warp the photo to make the board square using a tool such as Serif’s Affinty Photo) then place the photo scaled to actual size in a drawing program w/ the parts:
And, if one can’t find a suitable arrangement, then one can bag it and section the board and cut one part at a time (which seems to be what I’m going to be doing).