When you buy the latest micro:bit with sound, the box includes a handy cardboard template that you can cut out and use to hold the micro:bit and battery pack together. This makes it neat and easy to carry.
You don't need to have the micro:bit box to use the template though. We've published it on the micro:bit website, so you can download, print and have a go at making and customising them yourself.
https://microbit.org/get-started/user-guide/battery-pack-holder/