R.J.
We just always have food available. My son has from the time he was little had the bottom drawer in the kitchen for non-spoiling food, and the bottom shelf on the fridge door for his milk cups, yogurt, fruit, etc.
Feeding on demand worked so well as an infant, we just stuck with it. Ironically, or not, his natural eating patterns developed into exactly as nutritionists say we ALL should eat; 5 or 6 small meals a day.
I just use zipock twist and seal cups, or ziplock baggies, and fill them with whatever for being out and about.