There are many different JAYGO techniques for joining granny squares or other crochet motifs. I have previously written about Join-As-You-Go with picot and Join-As-You-Go with single crochet…so here is another method I often use – Join-As-You-Go with arches.
Using this method, we join motifs through the corresponding ch-3 arches while working the last round…so basically, when you need to join, just change the regular arch (ch-3) to joining arch (ch 1 + sl st + ch 1)….and the rest is the same.
In the diagram below, the first Granny Square has 20 regular arches in Rnd 5, but the second Granny Square has 14 regular arches + 6 joining arches (20 total).
Regular arch = ch 3
Joining arch = ch 1, sl st in corresponding arch of previously made square, ch 1
Here is my short video demonstration of this technique.