My method:

ROW 1: Ch 26. Sc in 2nd ch from hook and ea ch across, turn. (25)

ROW 2: No ch needed, sc in first (same) sc, * sk next sc, 3 sc in next sc, sk next sc, sc in next sc, rep from * across 6x, turn. (25)

ROW 3: No ch needed, sc in first sc and ea sc across, turn. (25)

Rep rows 2 and 3, ending on row 3, until piece is relatively square, 25 rows.

Border: Ch1, sc in same sc and around perimeter of cloth, with 2 sc in ea corner, sl st to first sc. Fasten off, weave in ends.