How do I hold my knife to prevent blisters when chopping?
Friction blisters are usually the result of continuous rubbing on skin that hasn't toughened up.

If you are getting blisters with normal amounts of chopping, either your knife is moving in your hand more than it should, or you are exerting more force than you should need.

Focus on your technique. Are you pushing down with the whole palm, the front of the palm, or the back of the palm? Are you guiding or forcing with your thumb and forefinger? Is your knife sharp and heavy enough for the materials you are cutting through? Are you using a circular motion to chop?