I'll slice you open like an envelope - This phrase means you're going to be cut up like a meat pie

This phrase means you're going to be cut up like a meat pie and you're not even worth the effort.

He said, "I'll slice you open like an envelope," then started screaming at my mom.

During the class, she said, "I'll slice you open like an envelope," and then drew on my desk.

He said, "I'll slice you open like an envelope," and then took my hoodie.