Generally speaking those go something like this.
Get some dehydrated foods. Or dehydrate your own.
Find a recipe or make up one yourself.
Put ingredients like veggies, rice, pasta, meat and seasoning in a plastic ziploc, vacuum bag, or mylar.
Store with an oxygen saver if for LTS.
Open bag pour contents into cup, bowl, thermos and wait for however long it takes to rehydrate.
Then enjoy.
These are a staple of the hiking and camping communities.
You can tailor them for people with dietary restrictions. Make them for breakfast, lunch, dinner.
Up the calorie content for strenuous activity.
Very flexible fairly cheap compared to the FD meals and you control what goes in.