Here is a great tip for sewing any of your blocks together.
Right after you sew your fabric together and it looks like this:
And before you open it up to press your seams open or a direction, PRESS YOUR STITCHES. Like so:
This helps to set your stitches a little better!
Then you can open your square:
And press your seams in the desired direction.
Tip of the Week: setting your stitches