You are right, natural feeding is much more complex than that. It involves combining natural foods to provide a rabbit with the nutrition they need, without using pellets.
Natural feeding usually involves one or more of the following:
Alfalfa hay
Grain
Sprouted fodder
Gathered forage.
Alfalfa hay and clover hay are not grass hays, and are much higher in protein than grass hays tend to be.
Grains like wheat, barley, and oats can also form the majority of a good diet.
Sprouted fodder involves taking grain and sprouting it, which completely changes its nutrient profile. It can be fed right after sprouting, or anytime up to about 8 days. Every day, the nutrient content is different, so the breeder will decide at which point they want to feed, and stick with it so the fodder is relatively consistent.
Forage is made up of gathered weeds and herbs which are known to be safe and nutritious.
A mineral block chunk is provided for salt and trace elements.
Natural feeding is not recommended to anyone just starting with rabbits. It takes a lot of study and attention to get it going well, and rabbits already have a good sized learning curve.
