This method is very similar to the flat braid join, except you do not drop lp from hook and pick it up again. This is faster and easier but does not give the twisted look of the flat braid join. Still, pretty and very useful. I've used this method way more than the flat braid join over the years, but now I find myself using the flat braid join more for the little extra beauty it gives, especially on special projects.
Work the scallop join just like the flat braid join, except on flat braid join where you (ch 2, drop lp from hook, insert hook in next ch-sp on first block, pick up lp, ch 1, sc in next ch-sp on second block), substitute this:
(Ch 1, sl st in next ch-sp on first block, ch 1, sc in next ch-sp on second block)
Here's how it looks: