Attach buttons to a border

Dear all,
I have made a baby sweater. But the pattern does not include making buttonholes and attaching buttons.
As a result the front is open and will stay so when the baby wears it.
So is there any way that I san sew on the buttons now on the garter st. border, I mean where do the buttonholes come from?

Maybe you could crochet loops on the edge? Or if the edges over lap, you can put in snaps. Maybe a zipper?

Button holes are usually knit in as you do the sweater–sometimes just a simple yo eyelet. If the knitting is loose enough, though, do you think you can slide a button between stitches?

Well, I have bought some cute little buttons.
It says you can glue, sew or use a button pin. Do you know what a button pin is?
For the buttonhole, I can use crochet, or may be just sew a ribbon loop. What do you think?

I think the crochet would be stretchier, but I have no experience with ribbon. I don’t know what a button pin is. I just sew. :wink: