Question: how to do huel diet?
Answer: Buy a big 'ol bag of Huel powder.
Scoop some Huel into a shaker. It's about 150 calories per scoop, so you put in as much as you need. ... 
Add water, or milk, or a plant-based milk replacement. Oat or rice milk work well.
Shake it.
Drink it. Your nutritional needs are met, voila!