Break Out

Mr. Machete?

If you place them in a vise and use pliers, clippers, etc. you will get plastic pieces all over the place and possibly in your face. Protective glasses will at least stop you from going blind. But cuts on your face are not fun either.
If you have a dremel type tool or a saber saw you can just cut the edges off and the thing will fall apart and no plastic pieces flying around.
If you do attempt to cut off the edges with any electric type of saw make sure you do not use a harsh toothed blade or a metal cutter blade. Hard or sparse teeth on the blade could also send pieces flying. Metal cutters usually create heat and the plastic reseals itself as the blade passes.
Of course you could just use a Propane torch. No possible pieces flying around at all.
Placed on an M-80 firecracker and then lit will eventually open the slab but finding it may be a problem.
Handing a slabbed coin to a teenager and telling them it can not be opened is also another sure fire method.

vice
hack saw

Gimme a six pac of beer and I will show you how to open up anything!

I thought slabs were meant to increase value?

You should make a video of opening up one and post it here

In reality those are plastic collectors. Since there are so many types of plastics being used today, people have found a new type of collecting. That is why they are opened so that the silly coin inside can be discarded and the valuable plastic can be saved.
In most there is a dirty little piece of something with writing on it that also must be properly discarded. As with batteries, all such coins and those little peices of things with writting on them must be carefully discarded so as not to hurt the invironment.

Sure. That's why the bluesheet for slobbed coins have prices about 20% lower than greysheet for raw coins that actually are the proper grade.