I use the SC to join squares myself as I think it is quicker than whipstitching. I like to lay out the entire afghan. Like this:
A B C D E
F G H I J
k L M N O
P Q R S T
I start at one end, P and Q for instance and, with wrong sides together, corchet those two squares together. Then, I take K and L, put the wrong sides together and SC those two together. Then F and G, then A and B.
I take the first strip and, starting at Q, join R with single crochet then continue with L to M, H to G, C to B.
I do this for the next two rows. Then, I start with O and T and crochet across that row. When I get to the first row of SC I slipstitch into it and continue the SC across the next square. This make a really pretty raised border. I finish up with a row of single crochet around the entire afghan and then a decorative row of sc in first sc and then triple crochet in next sc.