I am making a baby blanket where the middle is cable knit and then the stitches are picked up all around the blanket for a garter stitch border. Is there any way to pick up stitches so that there is no seam?
I don't know this pattern, but if I had to guess I'd say that they want you to pick up stitches so the garter edge ridges go longways along the edges.
If you don't mind a different look you could just add x number of stitches to the pattern and knit the edge as you are working. For example add 10 stitches and knit 5 stitches on each side for the border. If you do this don't forget to add some rows at the bottom and top to match.
When asking questions ALWAYS post the name and a link for the pattern if you have it.