How to crochet stacked single crochet stitches
What is stacked single crochet?
This is a way of repeating single crochet stitches on the same stitch, often used to replace ch 2 or ch 3 standing stitch, to create a smoother edge to the fabric without noticeable gaps.
This is the stitch I use in my design Komorebi.
How to crochet a stacked single crochet stitch

After finishing the previous row, turn it over, without crocheting any chain stitches, insert the hook directly into the first stitch, yarn over(yo), and pull out a loop.

Next, yo and pull thru all loops to complete the first single crochet(sc). Then, insert the hook into the left leg of the first sc(marked in red).

After insertion, yo, pull a loop.

Next, yo, pull thru all loops, 2nd sc completed, stacked single crochet finished..
Video demonstration of the stacked single crochet stitch