Cut the bra band out of a fabric as two separate pieces (not on a fold). If you make a strapless bra like this one, straighten the upper edge of the band. Make the two halves of a bra ready as advised in
Before threading the underwires in, attach a hook&eye tape on place and push a boning in both of them. Close the ends of the tape sewing by hand.
Although the bra has a front-closure it still has fastening on back as well. And, why so? It’s because of the adjustment and convenience in use.
So why have a front-closure at all? Because it’s a pretty detail, it gives great support especially to a strapless bra and you can use it if you prefer!