This is a fun stitch! I didn’t have all the right things to do it, so I improvised (story of my life!).
So grab your yarn, crochet hook, and something you can use to hold the loops up, I just used a knitting needle but anything cylindrical and long should be ok.
Start by chaining 21, and then sc across for the first 2 rows.
Now we’re starting the drop stitch part. Chain 1, and pull loop up to the height you want it, and then stick in on the knitting needle and off the hook. Insert the hook into the next stitch and pull yarn through, yarn over and pull loop though, draw loop up to height of working row and put it on the knitting needle with the previous loop. Continue across the row until you have all the loops.
Now that you have all these loops, you’re going to need to single crochet over the top of them.
Then you can switch between the 3 rows of single crochet and the drop stitch row. Once you’re done with the 3rd row of drop stitch you can do 2 more rows of sc and then your square should be done!