Somehow the slime propaganda has been extremely successful. People have forgotten how dangerous they are. They are most certainly not a "low level" monster. I don't know how the idea of a core even spread considering anyone who's seen a slime would know that's false.
An entity that is immune to physical damage, can split itself on the atomic level and recombine instantaneously... Without extremely high spatial affinity, a slime is unstoppable. Even with it, at most you'd be able to slowly imprison parts of it.
Do not engage, always leave as soon as possible.