If you don't want your clip to slide out, you can't line the back all the way up.
Here's a pic of mine. I used to line them all the way and they didn't work well (and were tough to line!) then I changed the way I do it and haven't had a problem since! I use High Temp Hot Glue.
Looking at the picture now (it's an older pic), I don't even line them that far up anymore (like the white one) I put ribbon just under the tip of the clip. Most of the clip shows on the underside, but they snap nice and tight now.