The current project I'm working on uses blocks of 9.5" x 9.5" ((churn-dash). On the square units (HSTs and half-squares), I'm pressing seams open and I think they are lying nice and flat. I tried a couple of blocks pressing the row seams to the side, but I think I prefer pressing open.
The blocks end up being about 9.25" and the edges are not quite even. Great suggestions bearisgray! I will try those.
I'm pretty confident that my cuts are acurate, And since my HSTs are cut to 3.5 x 3.5 after sewing (and my center block is 3.5 x 3.5), I suspect I'm off on my half-squares The suggestion on the strips will probably help me. I might try a narrow seam on those and then cut them to size.