It is actually really easy to add a crochet border too. I thought of two ways to do so. First you could add swiss entredeux (pictured here) in between the layers and cut off one of the fabric sides on the entredeux then use the holes as your initial chain stitch. Or you can do what I did on this blacket and use a large enough eyed needle to hand stitch with your color yarn around the border with a chain stitch (pictured here) . I made sure I went along the top of the edge and tried to keep the stitches equal in number and size on opposite sides. These chain stitches were used as if they were my initial chains I would have made if I was only hand crocheting. I hope this encourages some new ideas.
Enjoy,
Barbara