First step is removing the crust - after all, they're not called Crustables. You can choose to do this by simply cutting the crust off with a knife (making a square shape), using a sandwich de-cruster, a large biscuit cutter, or the method I use - a glass & a knife. I just flip a glass upside down, press down, and then go along the edge of the glass with a knife - making the round shapes you usually see in the store bought version. Spread a thin layer of peanut butter in the centers of each piece of bread - taking care to not let the peanut butter reach the edges so you can seal it properly.
Dollop about a scant teaspoon of jelly/jam/preserves in the very center of half of your slices of bread. Don't add too much because you don't want it oozing out when you seal them up. The other half of the bread slices should be just peanut butter.
Top each jelly centered piece of bread with a peanut butter covered one. Seal the sandwiches by pressing down along the edges with a fork, all the way around. They even sell sandwich crust removers that have a sealer too, so that’s always an option as well.
You can serve them as is - or you can put the into the freezer for easy lunches.To freeze, lay the uncrustables out on a large baking sheet & place in the freezer for 2-4 hours.
Once frozen, remove from the baking sheet & store in a large ziploc freezer bag. If sending them with your kid to school, remove from the freezer bag & place in their lunch - they will be thawed by lunchtime. If you are wanting to eat one straight from the freezer, simply place it in the microwave on the defrost setting for 30-60 seconds, depending on your microwave. (Start out at 30 seconds, and increase if needed)