I.C.
We had a Lunch Station at our house. There were several small baskets, each filled with a different type of food: chips in one basket, fruits in another, veggies in a third and so on. The baskets either had the item itself (like a cup of applesauce) or a picture of the item (like a cup of yogurt) if it was perishable. I used a small cork board to post pictures of available sandwhiches.
Every night after dinner, my sons were responsible for packing their own lunch from the baskets. When the boys were really young, I taught them to pick one thing from each basket; as they got older, I varied the numbers (unlimited fruits and veggies but only 1 chips for example). Actual items got placed in the lunch box while pictures were set on the counter by the fridge. The sandwhich picture also went there.
Before I went to bed (usually as a part of my after-dinner clean-up), I'd make the requested sandwich and place it in the fridge (if perishable) or lunchbox (if not).
The next morning, part of my kids' routines were to add the perishable items to the lunch box, return the pictures to their places and check off Make Lunch from their To-do list.
I started doing this with my oldest when he was 3 years old. It takes a certain amount of set-up of the Lunch Station and then training of your child on your part but, in the long run, it saves time and money and reduces arguements. I controlled what went into the Station's baskets but my son controlled what went into his lunch. He picked only those things that he felt like eating that day so less got thrown away. Time was saved because the lunch packing chores were divided in half between me and the boys.
As far as what to put in the various baskets or to offer for sandwhiches, the sky is the limit. It could be Lunchables or PBJ or crackers and cheese for the main course -- use whatever your child likes and whatever ideas you come across.
Some of the biggest advantages to this plan are long-term. First, my kids learned independence and decision-making skills. Second, I learned NOT to argue over the little things when it was possible to turn control over to the child (why should I decide on applesauce and then make him eat it when he'd prefer pineapple tidbits and eat it willingly?). My kids learned what makes an acceptable meal: small protein, unlimited fruits and veggies, sugar and fats sparingly. They learned to manage their time better and to make school preps the night before.
All in all, it was a good process for us.