I would say no sashing. It would ruin the secondary pattern, although sometimes those secondary patterns show around the sashing.
How about adding a half a row at the bottom to make it not square? You would have four blocks across and five down.

My thoughts exactly. I too prefer the secondary pattern you get when putting the blocks together without sashing.

Without sashing and make one more section to make it just a bit bigger for a nice sized lap quilt. I think that would be great. I love the design and I really love paper piecing. Are you going to do an outer border?

Love the colors and the pattern. Nice job with the pping. I like it without sashing. You could perhaps make it larger by adding a half block to all side and see what it looks like.
If you need to add but don't want to make more blocks I would put a small inner border of one of the colors and then a wider border of black.

Definitely no sashing!

No sashing. I would leave it that size and put it in the swap. It is lovely, but a bit too busy for my taste in a quilt on a bed.

I love it without sashing and I also would like to know the name of the block. Thanks for sharing.

I agree with everyone else - no sashing - and would definitely add some more blocks. Wall hangings just are not my "thing", but everyone loves lap quilts.

Depending on where you're going to use it, would determine if I go bigger or leave as is.

I say go big and no sashing. I like the way it looks.