With color, ch 4; join with slip st to form a ring. RND 1: (Right side) Ch 3, (counts as first dc, now and throughout), 2 dc in ring, ch 2, (3 dc in ring, ch 2) 3 times; join with slip st to first dc; 12 dc and 4 ch-2 sps.
RND 2: Slip st in next 2 dc and in next ch-2 sp, ch 3, (2 dc, ch 2, 3 dc) in same sp, ch 1, * (3 dc, ch 2, 3 dc) in next ch-2 sp, ch 1; repeat from * 2 times more; join with slip st to first dc, finish off; 24 dc and 8 sps.
OPTIONAL: I added a RND 3 repeating RND 2 for bigger squares.
Complete all squares in this manner.
ASSEMBLY
With matching color using Placement Diagram below and working through inside loops only, whipstitch Squares together, forming 15 vertical strips of 19 Squares each, beginning in second ch of first corner ch-2 and ending in first ch of next corner ch-2; then whipstitch strips together in same manner.
EDGING
RND 1: With right side facing, join yarn with sc in any corner ch-2 sp; ch 2, sc in same sp, (sc in next 3 dc or 4 dc if you added a round and in next sp) twice, hdc in joining, (sc in next sp and in next 3 or 4 dc) twice, [sc in next sp, hdc in joining, (sc in next sp and in next 3 or 4 dc) twice] across to next corner ch-2 sp, * (sc, ch 2, sc) in corner ch-2 sp, (sc in next 3 or 4 dc and in next sp) twice, hdc in joining, (sc in next sp and in next 3 or 4 dc) twice, [sc in next sp, hdc in joining, (sc in next sp and in next 3 or 4 dc) twice] across to next corner ch-2 sp; repeat from * 2 times more; join with slip st to first sc; 676 sts and 4 ch-2sps.
RND 2: Slip st in first ch-2 sp, ch 1, (sc, ch 2) twice in same sp, skip next sc, (sc in next st, ch 2, skip next st) across to next corner ch-2 sp, * (sc, ch 2) twice in corner sp, skip next sc, (sc in next st, ch 2, skip next st) across to next corner ch-2 sp; repeat from * 2 times more, join with slip st to first sc, finish off.
Referring to the "KEY", make the number of Squares specified in the colors indicated (or your colors of choice)