For the strap, I decided to use the same stitch which I crocheted flat like so:
(evening photo, the colours are off)
Then I sewed it up like a tube which makes for a nice firm strap with more body than if I'd just used one layer. I wasn't sure how to attach it to the bag: if I'd sewed it up at the ends, it would have pulled too much on the crochet fabric when the bag was full. Sometimes these metal closures have rings to attach a strap to but this one didn't. So I ended up sewing it as far down each side as I could (taking into consideration the curve of the clasp), sewing first into the crochet fabric and then right into the holes of the closure too.
I will be adding a plastic base to it as I did to my little black back. I also want to line it but I don't currently have any fabric to match. I shall get some this week.
I will use it and see how I feel about it. My mother-in-law exclaimed how much she liked the bag when she saw it so I will have to make another one in green (her favourite colour). She did say how wonderfully old-fashioned it looked and the kind of bag they use to have (which reinforced my view expressed at the beginning of this post!).
I think I'm going to search for a large square closure of that type too, wondering if that would look a bit more modern and up-to-date. The closure really is very practical… maybe I just need to get used to the look of it. We'll see.