Love your blocks!

I'd say start with whatever center you want and then add some sashing with the smaller blocks, stagger the sashing so it is not side by side. No one will ever notice - this idea was in a pattern at a class and it worked.

Not sure I understand "stagger the sashing so it isn't side by side". Do you mean make each row of sashing whatever width needed to make everything fit? Hope I'm not sounding too dumb, but it's a rainy day here and that affects my brain! :-(

nice