We do things similar to those already mentioned:
1. Buy things that are on sale and figure out what to eat based on what we already have stocked, which means we only have to buy produce or the like (from Aldi if we can help it) to fill out the meal.
2. We went through a period a few years ago where money was tight, so we cut back on meat, then realized we didn't really miss it as much as we thought we would. We went from meat for dinner every night to going veggie at least a few nights a week (with one day for fish).
We also...buy chicken off the back of a truck.
It sounds weird, lol, but it's through a company called Zaycon, who functions sort of like Costco except they sell directly to consumers. My co-worker and I go in together once or twice a year for a 40 pound box of chicken, one of us picks it up off the refrigerated truck at the pre-determined place/time (they don't have a storefront), split it for 20 pounds each, and freeze it for whenever we need it. We're only a two-person household but it would be great for large families. We've also gotten ground beef and bacon for great prices, and they have other products like honey, milk, salmon, etc, depending on the area you're in.
Here's their general link:
https://zayconfoods.com/Here's my referral link, just in case (I just get a dollar per person who makes a purchase; I don't work for them or anything):
https://zayconfoods.com/refer/zf41287