How do I sew up an afghan?

Hi
I’m just putting together some square swatches to make a rug/afghan and am wondering if there is a way to sew the edges so there isn’t an obvious seam at the back as you’d get sewing up a garment if you use anything like mattress or backstitch? Some of the edges are garter bordered and others are moss stitch. I’ve never done this before but am sure there is an afghaner out there who has a great tip for this or a technique I don’t know about.
Looking forward to hearing your helps!
Thanks, Jan

http://www.knitting.co.nz/site/page_affix/toaffix_learntoknit13/

Try the edge-to-edge seam.

Thanks Ingrid, do you think an edge-to-edge seam would be strong enough? I wondered about trying something with a crochet seam? any thoughts?

I single crochet mine together. It does make a ridge, but after you wash it, the ridge lays relatively flat.

Thank you for these ideas, I think the crochet edge might be stronger and look a wee bit better. Thanks again, Jan