This is by FAR the hardest so here you go:
What you will need:
Cutting mat or board
IF you do not have a hammer, you will not be able to break the bathbomb at the seam.
Take the bathbomb on its side and place the knife right on the seam. Next you take the hammer and tap lightly to make a dent with the knife. You can start adding harder taps as you get farther down. Then it should break. It may not break in half perfectly, but that's okay. you can use the excess in the bath too. Just remember to put it in a Ziploc too! This was my finished Avobath:
Next put both halves in different plastic baggies and you should be set!
You can store everything together or separate, I have never notice smells meshing. I have everything in a plastic tote in my closet!
Breaking down bathbombs makes the bombs last longer, especially if you have a small apartment tub.