Sewing together squares knitted on the bias

Hi everyone, I’m new here. I’ve been knitting for 34 years (since age 5) but my finishing lets me down a bit. I’m knitting a popular baby blanket done in squares, four squares make a large square with the centre part like four petals or leaves maybe. I’ve managed to make a good job of sewing the little squares into bigger squares, now I’ve got to join twelve large squares into four rows of three, I’m having a problem doing it neatly, the smaller squares were easy as they were mainly joining garter stitch, the larger ones are a mix of garter stitch, stocking stitch and little eyelet holes and I think the reason I’m having trouble is that the squares are on the bias so no neat straight edge to follow, the increases and decreases at the ends of the rows make life harder. Anyone got any tips on the best way to do this? I’ve been using a mattress type stitch and now I’ve got my four rows of three to join and it’s getting even harder! All advice appreciated, thanks.

I’ve tried several different seaming methods for afghan squares, and prefer to do a simple whipstitch. I didn’t think it would look good before I tried it, but it always works for any kind of knitted or crocheted fabric. It creates a nice, reversible join. I do the whipstitch on the right side of the fabric.

I used it for this afghan, with purple yarn:

Hailey Blanket Complete 3 by Shandeh, on Flickr

Hailey Square by Shandeh, on Flickr

And for this one in Kiwi green:

Lime and Chocolate - Hat and Blanket Angled by Shandeh, on Flickr

And for this crocheted afghan in white:

Seaming Going Well by Shandeh, on Flickr

Border by Shandeh, on Flickr

Blanket Complete by Shandeh, on Flickr

Thanks for that, will give it a go!