1. Back the embroidered blocks (easier done before embroidery next time) with a VERY lightweight one-sided-fusible interfacing. Trim to your required size.
2. Use a similar or even slightly different fabric for enlarging. Cut strips to length to match 2 sides (the width you need), and add them to opposite sides. Re-measure and cut strips for the remaining two opposite sides, and add them. Square up the enlarged blocks yet again.
Now you are ready to set with your alternate blocks. If you feel the seams are too thick upon joining these blocks, you might try pressing the seams open.
Be sure to let us see the finished top!
Jan in VA