Heating Meals

This question was asked by Adam W 
Do these hot pack meals need to be placed on a level surface while heating or can they heat while you are on the go?  https://www.thebewellgroup.com/search?q=hot+pack+self+heating

Ideally a surface that is as level as possible is best, but it does not need to be perfectly flat, while it is re heating the meal, you need the water to be
around the whole meal for best results.