Round 1:  Work 1 Half Double Crochet (HDC) into each stitch, work 3 HDC into the corner spaces, and work 1 HDC per row. Join with a slip stitch at the end of the row to the first HDC.  

Working in the same direction, chain 9, In the third chain from the hook, work HDC and then work HDC into each chain for a total of 7 HDC. Slip stitch into the next stitch that is on the border and the next stitch, turn, skip over the slip stitches and work 7 HDC into the back loops of the HDC you just made down the chain. CH 2 and turn. Work 7 back loop only HDC back down to the edge of the blanket, slip stitch into the next two spaces. Repeat in this manner down the side of the blanket.

When you reach the corner, instead of slip stitching over two times, slip stitch into the corner space three times in a row. Meaning, after you work up and down the HDC’s, slip stitch back into the same corner space, repeating three times. This will fan the work around the corner. Then you return to slip stitching over the next two spaces.

When you have gone all the way around the blanket, finish the last corner by slip stitching 3 times into the same space, then end on the outside edge of the blanket. Tie off leaving a long tail. Sew the last edge to the first edge of the border. Then weave in all remaining ends.

Watch video below around the 14 minute mark for further help.