When both my dogs were puppies, I put painters' tape on the floor of the kitchen entry points. With "sits", "outs", and treats, they quickly learned not to cross those lines if someone's in the kitchen. After a while, tape comes off, they stay behind the imaginary lines.
Have always feared dropping boiling water or a knife on a dog. Have done it to myself, extra hazardous if you're carrying something and don't notice the pet by your feet.