In a large bowl, mix together baking soda, citric acid, and epsom salt together.
The consistency will be crumbly, at this point it's ready to form!
You can form it into half spheres with the ice cream scoop and lay them out to dry on a cookie sheet over night. Make sure you really pack the scoop full, and compact it down.
If you need the perfect circle bomb shape, you may want to hunt for a silicone mold from amazon or a craft store.
If you are here for the experience, form them in a muffin tin mold with the paper, and leave them in the mold at least 12 hours to firm up before removing.