Sewing side seams when the rows don't match

I’m working on a drop stitch pullover which is worked in two big squares. I’m up to the point where I need to sew up the sides to create the armholes, but I’m not sure how to seam it.

Pretty much everywhere recommends mattress stitch, but the problem is that my rows of garter and drop don’t line up (this is entirely my fault due to mistakes)

All the tutorials on backstitch I’ve found are for horizontal seaming, and these are done vertically.

It’s a side seam so it doesn’t have to be invisible, just neat.

You can use a back stitch for vertical seams as well as horizontal. Line up the garter sections as best you can and pin in place. I often use back stitch for side seams when mattress stitch isn’t the best choice.

Thank you! I wasn’t aware it was for both :sweat_smile: