i just finished a quilt for my dgd which we designed ourselves. We wanted 2" sashing so I cut the strips 2.5 inches lengthwise to get the most out of the fabric. She is 15 and this was her first project. She sewed the sashing in place with a little help pinning since some blocks were off a little, (can't believe that!) and it actually came out great! After washing, who could tell! good luck with yours! I would say it doesn't matter which way you cut. I try to be thrifty! This was my 5th quilt for gkd's and I have cut all sashing that way. Hope this helps.