I’ll start with the photos I wanted to upload yesterday.
Here is D-5 before the border was added:

and here is D-5 after the border was completed:

Now to the penultimate square, C-1.
The directions began well enough, exhorting the crocheter to start “at center with first color, ch 4, sl st to first ch to form ring.” After that, however, the directions have little relation the square pictured, so I did the following:
Round 1: Ch 3 (counts as first dc), work 11 dc into the ring, join with sl st to first dc (do not fasten off yet) (12 dc)
Round 2: Ch 3 (counts as first dc) work 1 dc in same st as joining, *work 2dc in next st, repeat from * 10 times more. Join with slip st to first dc. Fasten off. (24 dc)
Round 3: With a new color, work a lsc (long single crochet) to the right of any 2-dc group, ch 2, *work a lsc to the right of the next 2-dc group, ch 2, repeat from * 10 times more. Join with sl st to first lsc made. Fasten off.
Round 4: With a new color work an hdc in any lsc, work 3dc in each of the next 3 ch-2 sp, **work an hdc in the next lsc, work 3dc in each of the next 3ch-2 sp, repeat from ** twice more. Fasten off.
Round 5: Work (3dc, ch3, 3dc) in any hdc, sk next dc, 1 hdc in each of next 2 dc, 1 sc in each of next 3 dc, 1 hdc in each of next 2 dc, sk next dc, *Work (3dc, ch3, 3dc) in next hdc, sk next dc, 1 hdc in each of next 2 dc, 1 sc in each of next 3 dc, 1 hdc in each of next 2 dc, sk next dc, repeat from * twice more. Join with sl st to first dc made. Fasten off.
Round 6: Begin with a new color in any corner, *work 2sc in ch-3 sp, 2sc in next dc, 1 sc in each of next 11 sts, 2sc in next st, repeat from * 3 times more. Join with sl st to first sc. Fasten off.
Corners:
Row 1: With the right side facing, attach yarn with a sc to the third sc from the right of any corner. Sc in the next 12 sts. (13 sc) Ch 1, turn.
Row 2: Sc first two stitches tog. Sc in next 9 st, sc tog last two stitches (11sc). Ch 1, turn.
Row 3: Sc first two stitches tog. Sc in next 7 st, sc tog last two stitches (9sc). Ch 1, turn.
Row 4: Sc first two stitches tog. Sc in next 5 st, sc tog last two stitches (7sc). Ch 1, turn.
Row 5: Sc first two stitches tog. Sc in next 3 st, sc tog last two stitches (5sc). Ch 1, turn.
Row 6: Sc first two stitches tog. Sc in next 1 st, sc tog last two stitches (3sc). Ch 1, turn.
Row 7: Sc next 3 sts tog. (1 sc). Finish off.
Repeat with the 3 remaining corners.
Border:
Round 1: Attach new yarn the top of any of the triangles just completed (Ch 3 counts as first dc) *at the top of the triangle work (3dc, ch 3, 3dc), working along the side, evenly space 8 3dc groups, repeat from * 3 times more. Join with sl st to first dc made. Finish off.
Here is what mine looked like after all was said and done:

Related post: Better Homes and Gardens Crocheting & Knitting Granny Sampler blog posts