Last night I completed the final square for the sofa bed afghan! Now all that remains is to join them all together. I purposefully left off the final round on each square, so I could join-as-you-go with the final round once all of the squares were completed. I figured this would be easier than sewing or crocheting them all together afterwards, plus leave a neater seam between each block. One quiet evening a few weeks ago, when I had the house to myself, I sat down with a spreadsheet and figured out how to do it.
Starting at the top right corner (meaning a large square was the final square to be completed) I will crochet the final round following the arrows on the diagram. Each time I pick up a new square to add, I will weave in the ends so that I don't have a mammoth task of end weaving waiting for me when I finish. This is slowing down the process somewhat, but I think it's the best option.
So far I have joined two squares! I am hoping there is enough yarn left in the charcoal ball to do all of the join-as-you-go; I have plenty left of the brown, cream and purple so if I don't have enough charcoal left for the border, I will do it in those instead.
In case you were wondering, the numbers around the outside of the join-as-you-go diagram were me trying to count how many stitches I would have on each edge, so I could figure out which border patterns would work!