Sewing fabric to knitting?

I’ve almost completed a baby blanket for a friend (knitted). I want to sew on some flannel to the back of the blanket, but I’ve never sewn fabric onto something knitted before. What is the best way to go about doing this?

There are some instructions here -

What a cute blanket! I saw this some time ago but now that I’m expecting a boy this Sept. I may just have to make it. Thanks for the reminder!

That went right into my que Jan, Thanks!!