Step 1: To edge the first block, join with sc in any corner, ch 3, sc in same sp, (ch 3, sc in next ch-sp) around with (sc, ch 3, sc) in each corner ch-sp, join. Fasten off.
Step 2: Join with sc in ch-sp below top left corner, and work edging rnd same as step 1 around left edge, bottom edge and right edge to top right corner. Sc in top right corner, ch 2, remove hook from lp, insert hook in bottom right corner of first block, pick up dropped lp, ch 1, sc in same corner on second block.
Step 3: * Ch 2, remove hook from lp, insert hook in next ch-sp on bottom edge of first block, pick up dropped lp, ch 1, sc in next ch-sp on top edge of second block. Repeat from * across to corner; repeat in corner to be sure you connect corner to corner and have two sc in each corner.