I usually determine how wide my sashing needs to after I finish the center, If I ran out of fabric, and the tops not wide enough, it gets lots of sashing... if I'm doing something 'on point' then maybe only wide enough to keep me from mangling the edges. Or, if I think the top needs more color, ... you guessed it! I add another sashing! I recently saw a book in the library ,, Haffe Kassett , Kaffe Hassett???? anyway,... there was a photo of a quilt, so simple I don't know why I didn't think of it! like a modified log cabin! started with a small rectangle then strips on each side, the same color for each 'round' radiating out . Beautiful! the perfect sashing!