Crochet waffle stitch
US dc and front-post dc create a recessed grid.
Counted practice swatch
Chain 23. Work dc in fourth chain and across: 20 dc plus the counted ch3 = 21. The repeat is a multiple of 3.
Work the repeat
Row 2: ch2 (does not count), dc in first stitch; [front-post dc around next post, dc in next 2 stitches] 6 times; front-post dc around next post, dc in top of ch3. Row 3: ch2, turn, dc in first; [dc in next, front-post dc around next 2 posts] 6 times; dc in next 2. Repeat rows 2–3.
Read the fabric
The first and last positions are plain dc. Post stitches replace a top-loop stitch; do not work a second dc into the same post’s top.