Probably simple; felted bag question

I’ve been knitting a bag, merrily along. When I got to the point of doing the handles, I suddenly became stumped.
Here’s the handle instructions: On the beginning of round, K13, slip marker off, K3, bind off next 13 stitches, K3, slip marker off, repeat once more leaving only beginning round marker. (I got this all done just fine)

Here’s the rub: On next round, K16, cast on 25 stitches, K16, cast on 25 stitches, knit to end of round. Work 4 more rounds, bind off.

How do I cast on more stitches in the middle of a work in progress? On the left needle and then slide them over to the right needle?
Thanks for any help!

You can use any one of the single-strand cast ons. Backward loop and knitted cast-on work well in this case.

Just get to the point where you need to cast on, use your working yarn to do so, then continue with your pattern.

Thank you Ingrid! I got it done using the backward loop and it’s in the washer now.