How would I do a leaf edging in the round on a square shawl?

I would like to make a leaf-style edging (similar to the tulip edging in Barbara Walkers Second Treausury or the leaf edging in Field Guide to Knitting) around a shawl. I think that I would just pick up and knit all around the sides of the shawl, but I am confused about what to do at the corners of the shawl. What stitch should I do at the corners of the shawl. I thought that I would just have one knit stitch on each side of the first row, but I am concerned that this will be stockinette in the round and will roll. I hope that my question makes sense. I understand how I would do the pattern in the round, EXCEPT for the corners. Do I do a mitered stitch? If so, how do I do this.

I’m confused as to whether you want to knit an edge in the round, or knit an edge perpendicularly AROUND the square.

But in the first case, you would miter the corner by adding a stitch to each side on either side of each corner, every other round. (Each side grows by two stitches every other round)
You can work in whatever pattern stitches fits to the “extra” stitches, or just leave them plain.

If you are working aperpendicular edge around the square, then usually what you do is take half the number of stitches in the rows of the pattern in ease either side of the corner. For example : if your edge is an average of 8 stitches per row, from 4 stitches before the corner to four stitches past the corner attach the edge only on *every OTHER *inward row. This gives you extra edge pattern to ease around the corner so that it will lay flat and not cup.

The wider the edge, the more ease you are allowing.