If you are still looking for advice -
I am a miniaturist and I use down to 3/4" squares.
so -
Be as accurate as you can with every step.
Measure every time you join squares together so if one is off and you need to adjust you can do it now instead of
seeing how off it is down the road.
I tack the corners so they can't move. This is a stitch or two on the side where the seam will go through.
I iron every time I join anything. the more you iron the easier it is to join squares. If the fabric isn't flat it is harder
to handle in my opinion.
If working with small squares - I like to sew 4 together and then continue with 4 patches and then sew the 4 patches together. it gives you more to hang onto and makes it easier to handle.
When you sew single rows at a time it is easy to get off some in your size. You can end up with 2 rows that are different lengths when done. the 4 patches helps to keep from skewing the squares as you join them.