Wash and hull strawberries: Rinse the strawberries under cold water, remove the stems and hulls, then slice them.
Prepare the Clear Jel mixture: In a medium saucepan, whisk together the granulated sugar and Clear Jel.
Add water: Gradually add the water to the sugar and Clear Jel mixture, whisking continuously to prevent lumps from forming.
Cook the mixture: Cook over medium heat, stirring constantly, until the mixture thickens and begins to bubble. This will take about 10-15 minutes.
Add lemon juice: Stir in the bottled lemon juice and cook for an additional 1 minute, ensuring the mixture is smooth and thick.
Add strawberries: Gently fold in the sliced strawberries and, if desired, a few drops of red food coloring to enhance the color.
Heat the filling: Continue to cook for another 5 minutes, stirring gently, until the strawberries are heated through.
Prepare jars and equipment: Sterilize the mason jars and lids by boiling them in water for 10 minutes. Keep the jars hot until ready to fill. Prepare your water bath canner by filling it with water and bringing it to a simmer.
Fill the jars: Using a canning funnel and ladle, carefully fill the hot jars with the hot strawberry pie filling, leaving about 1 inch of headspace at the top.
Remove air bubbles: Use a bubble remover tool or a non-metallic spatula to remove any air bubbles by gently stirring around the inside of the jars. Adjust the headspace if necessary.
Wipe the rims: Wipe the rims of the jars with a clean cloth or paper towel to remove any residue.
Seal the jars: Place the lids on the jars and screw on the bands until fingertip-tight.
Process the jars: Place the filled jars into the water bath canner, ensuring they are fully submerged with at least 1 inch of water above the jars. Bring the water to a rolling boil. Process the jars in the boiling water for 20 minutes (adjusting for altitude if necessary).
Cool the jars: Carefully remove the jars from the canner using a jar lifter and place them on a towel or cooling rack. Allow the jars to cool undisturbed for 12-24 hours.
Check the seals: After the jars have cooled, check the seals by pressing down on the center of each lid. If the lid does not pop back, the jar is sealed properly. If any jars did not seal, refrigerate and use them within a few weeks.
Label and store: Label the jars with the date and contents, and store them in a cool, dark place. Properly canned and sealed strawberry pie filling can last up to a year.