The first two rounds create the square in the corner of this mitered granny square.
Foundation, color A - Ch4, sl st in 1st ch to join.
Rnd 1 - Ch3 (counts as dc), 2dc into the ring, ch2, * 3dc, ch2, rpt from * 2 more times, hdc (counts as a ch-2 sp) into the top of ch-3 to join, turn. [12dc, 4 x ch-2sps]
Rnd 2 - Ch3, 2dc into the ch-2 sp, ch1, * (3dc, ch2, 3dc) into the next ch-2 sp, ch1, rpt from * 2 more times, 3dc into next ch-2 sp, ch2, hdc (counts as ch-2) in top of ch-3 to join, cut yarn and fasten off, turn. [24dc and 4 x ch-1 sps, and 4 x ch-2 sps]
Rounds 3 - 8 form the miter of this square and the rounds are worked on two sides of the square.
Rnd 3, color B - Ch3 (counts as a dc), 2dc in ch-2 sp, ch1, 3dc in ch-1 sp, (3dc, ch2, 3dc) in ch-2 sp, ch1, 3dc in ch-1 sp, 3dc in ch-2 sp, turn. [18dc and 4 x ch-1 sps, 1 x ch-2 sp]
Rnd 4 - Ch4 (counts as 1dc and ch1), (3dc, ch1) in the next 2 ch-1 sps, (3dc, ch2, 3dc) in ch-2 sp, ch1, (3dc, ch1) in the next 2 ch-1 sps, 1dc in top of ch-3 of prv rnd, turn. [20dc and 6 x ch-1 sps, and 1 x ch-2 sp]
Rnd 5, color C - Ch3 (counts as dc), 2dc in same sp, ch1, (3dc, ch1) in the next 2 ch-1 sps, (3dc, ch2, 3dc) in ch-2 sp, ch1, (3dc, ch1) in the next 2 ch-1 sps, 3dc in ch-2 sp, turn. [24dc, 6 x ch-1 sp, 1 x ch-2 sp]
Rnd 6 - Ch4 (counts as 1dc and ch1), (3dc, ch1) in the next 3 ch-1 sps, (3dc, ch2, 3dc) in ch-2 sp, ch1, (3dc, ch1) in the next 3 ch-1 sps, 1dc in top of ch-3 of prv rnd, turn. [26dc, 8 x ch-1 sps, 1 x ch-2 sp]
Rnd 7, color D - Ch3 (counts as dc), 2dc in ch-1 sp, ch1, (3dc, ch1) in the next 3 ch-1 sps, (3dc, ch2, 3dc) in ch-2 sp, ch1, (3dc, ch1) in the next 4 ch-1 sps, turn. [30dc, 8 x ch-1 sps, and 1 x ch-2 sp]
Rnd 8 - Ch4 (counts as 1dc and ch1), (3dc, ch1) in the next 4 ch-1 sps, (3dc, ch2, 3dc) in ch-2 sp, ch1, (3dc, ch1) in the next 4 ch-1 sps, 1dc in top of ch-3 of prv rnd, turn. [32dc, and 10 x ch-1 sps, and 1 x ch-2 sp]
Border this is worked around all four sides of the mitered square.
Rnd 9, color E - Ch3 (counts as dc), 2dc in ch-1 sp, ch1, * (3dc, ch1) in next 4 ch-1 sps, (3dc, ch2, 3dc) in ch-2 sp, ch1, rpt from * 1 more time, (3dc, ch1) into each of the next 4 turning ch-3 sps, (3dc, ch2, 3dc) in ch-2 sp, ch1, (3dc, ch1) into each of the next 4 turning ch-3 sps, (3dc, ch2) in last corner, sl st in top of ch-3 to join, ch1, cut yarn and fasten off. [72dc, 20 x ch-1 sps, and 4 x ch-2 sps]
Finish - Use a yarn needle to weave in the loose ends and if necessary block the squares to ensure that they are of an even size and shape to make joining easier.