Swapped Snowball Blocks & True Blue Block Party

Sample photo of my swapped blue snowball blocks from several years ago. I swapped enough to make two very large quilts. The swap allowed other colors in the blues.
For the Block Party we are using true blues, no other colors.
Below shows some of my cut blues. Baby blue, medium sky blue, dark and navy blues. Corners are creams. I'll be mixing the blues around to get six blocks to mail by end of month.
I found that to get true square corners it is better to press the corners open before trimming. If you cut the background away first then how do you see if the corners are square?
Trimming after pressing the corner square back. Saw the tip on Simply Quilts.

One completed 12.5 inch block for Block Party. Five more blocks to go. These will be sewn between working on the next deadline quilt top.