Base rnd, each side: Multiple of 8 + 7 + corner sts.
Begin 1 st to left of corner st.
Rnd 1: Ch 3 (counts as dc), dc in each st around, placing 5 dc in each corner st, join with slip st to top of ch-3.
Rnd 2: Ch 3 (counts as dc), *[skip 2 dc, FPtr around next dc, dc in 2nd skipped dc, dc in next 2 dc, FPtr into same dc as previous FPtr, skip 1 dc, dc in next 3 dc] to corner st, (FPdc, 3 dc, FPdc) in corner st — corner group made, dc in next 3 dc; rep from * around, omitting last dc, join with slip st to top of ch-3.
Rnd 3: Ch 3 (counts as dc), *[FPdc in next st, dc in next dc, Popcorn in next dc, dc in next dc, FPdc in next st, dc in next 3 dc] to corner group, FPdc in next st, dc in next dc, (dc, Popcorn, dc) in corner st, dc in next dc, FPdc in next st, dc in next 3 dc; rep from * around, omitting last dc, join with slip st to top of ch-3.
Rnd 4: Ch 3 (counts as dc), *[dc in next 2 sts, Partial FPtr in previous FPdc, partial FPtr in next FPdc, yarn over and pull through all 3 loops on hook — FPtr2tog made, skip Popcorn, dc in next 5 sts] to 3 sts before corner st, dc in next 3 sts, 2 dc in corner st, Partial FPdtr around previous FPdc, Partial FPdtr around next FPdc, yarn over and pull through all 3 loops on hook, 2 dc in same corner st, dc in next 6 sts; rep from * around, omitting last dc, join with slip st to top of ch-3.
Rnd 5: Ch 1, Reverse sc in each st around, join with slip st to first Reverse sc. Fasten off.