DC5TOG– double crochet 5 together:
Yarn Over (YO), insert hook, YO, pull back through, YO, pull through two loops, *YO, insert hook into SAME space as before, YO, pull back through, YO pull through 2 loops. Repeat from * 3 more times. YO and pull through all 6 loops.
Round 1: Work 1 SC (or HDC if you’d like) in each stitch around edge of blanket, working 3 stitches into the corner spaces. Join at the end of a round with a slip stitch, chain 3 and turn.
Round 2: *In the first of those chain 3’s, work DC5tog. Slip stitch (SLST) into the next 3 stitches (or however many you wish if you’d like the dots more spaced), repeat from the * and work around the entire blanket.
You do not need to do anything special around the corners unless you need to possibly slip stitch one or two less if you feel the blanket pulling and puckering.
Watch this video for a tutorial and work a practice swatch: