Wash your canning jars with hot, soapy water and keep them warm while preparing the jelly. Place the jar lids in a small saucepan and let them simmer lightly on the stove. Fill your water bath canner or a large pot about halfway with water, and let it come to a simmer as you proceed with making the jelly.

In a food processor, add the jalapeño chiles (half with seeds removed), along with the diced red and green bell peppers. Pulse until the mixture is finely chopped but not pureed. Transfer the chopped peppers to a mesh strainer and drain off any excess liquid to prevent the jelly from becoming watery.

Place the drained, chopped peppers (from Step 2) into a large stockpot. Add the granulated sugar, distilled white vinegar, and salt. Stir well, then bring the mixture to a boil over medium-high heat. Continue boiling, stirring occasionally, for 10 minutes. I find that stirring often prevents the sugar from scorching and gives the jelly a cleaner taste.

After the mixture has boiled for 10 minutes, add the liquid fruit pectin. Continue boiling for exactly 1 more minute, stirring constantly. Remove the pot from heat once the minute is up.

Carefully ladle the hot jelly into your hot, sterile jars, leaving about 1/4 inch of headspace at the top. Wipe the rims of the jars with a damp paper towel to ensure a clean seal. Place lids on top and screw on the rings just until you feel resistance, then give a 1/4 turn more. This ensures a secure but not overtightened seal.

Gently place the filled jars onto the rack in your simmering water bath canner. If needed, add more hot water so the jars are covered by at least 1-2 inches of water. Bring the water to a full boil, then process the jars for 10 minutes. (If you're above 1,000 feet elevation, add 1 minute for each additional 1,000 feet.)

Carefully remove the processed jars from the water bath and place them on a kitchen towel, spacing them about 1 inch apart. As the jars cool, you should hear a 'pop' as they seal. Leave them undisturbed for 12-24 hours. Jelly that has sealed properly can be stored on the shelf, while any unsealed jars should be refrigerated. I like to let the jars sit for the full 24 hours—this helps the jelly set up perfectly and makes for easier cleanup if any have failed to seal.