I worked the square as written through round 9. In round 10, instead of putting 5tr in the same stitch, I put 2tr, ch2, 2tr in the 4 stitches with those instructions.
For round 11, I did all 4 sides in sc, skipping the first stitch of each side after the corner, with corners as 2sc, ch2, 2sc.

The next row was(blue) bpdc with hdc in the corners, the next (silver) was crossed DC stitches, followed by another row of (blue) DC to bring my stitch count to 42 st per side.

I then did rows 19-29 of the Charlotte square pattern, and finished with a row of sc to bring it to 64 st, then dc all the way around for a total of 68 st per side.