Here's An Easy Way To Vacuum Seal Your Food
Sometimes you might think it could actually be worth buying a vacuum sealer. Vacuum-sealing food can help prevent freezer burn, keep pantry staples fresh longer, and ward off spoilage due to exposure to air (via Serious Eats). The storage method can actually be really helpful while cooking too. Removing all of the air around the food improves the distribution of marinades and can even slow down cooking during sous vide. However, it's entirely possible that it really isn't a necessity for you if you wouldn't use it often enough.
Kitchen vacuums can be costly, but you can avoid buying yet another kitchen appliance with a simple trick. Everything you need to vacuum seal your food is already in your kitchen because you can use water displacement as a vacuum seal. So, if you don't plan to store or cook food using this technique every day or even every week, then you can master this method and skip buying one more thing.
How to vacuum seal without a machine
To vacuum seal food with basic materials from your kitchen, all you need to do is fill a large bowl with water. Keep a towel handy so you can dry the bag when it comes out of the water bath, too. To start the process, turn the sealing seams of a freezer-safe plastic bag inside out so there's a cuff around the edge. This will help keep any liquid or food from getting into the seal which could compromise it (via Simply Recipes).
Next, add the food to the bag. It's best if you can arrange it in an even layer so the food will freeze or cook evenly. Using your hands, press out as much air as you possibly can and close most of the bag's seal, leaving the corner of one side open. Place the bag in the water while holding the open corner. Use your free hand to smooth out any air bubbles that might appear. Once all of the air is pressed out while most of the bag is underwater with the exception of the open corner, use your fingers to press the last bit of the seal shut.
The plastic should completely conform to the food inside when you're done. So, if it seems loose when you remove it from the water, give it another try. After drying the bag, you can store or sous vide the food inside without any air trapped at all.