Step 1: Gather fresh dandelion flowers from a clean, pesticide-free area, preferably in the morning after the dew has dried. Separate the yellow petals from the green parts of the flower. Discard all green bits as they can impart a bitter flavor. You should have 4 cups of packed yellow petals.
Step 2: Place the dandelion petals in a heat-proof bowl or jar. Pour 4 cups of boiling water over the petals, ensuring they are fully submerged. Cover and let steep for at least 4 hours, or preferably overnight, to create a strong dandelion 'tea'.
Step 3: Strain the dandelion infusion through a fine-mesh sieve lined with cheesecloth into a clean bowl. Squeeze the cheesecloth firmly to extract all the liquid. You should have approximately 3 to 3.5 cups of dandelion liquid. Discard the spent petals.
Step 4: Prepare your canning jars and lids: Wash jars and bands in hot soapy water; rinse well. Sterilize jars by boiling them for 10 minutes. Keep jars hot until ready to fill. Place new canning lids in hot (not boiling) water to soften the sealing compound.
Step 5: In a large, heavy-bottomed pot or Dutch oven, combine the dandelion liquid, granulated sugar, and fresh lemon juice. Stir constantly over medium-high heat until the sugar is completely dissolved. Bring the mixture to a full rolling boil that cannot be stirred down.
Step 6: Once a full rolling boil is reached, immediately add the liquid pectin. Stir vigorously for exactly 1 minute, maintaining the rolling boil. Remove from heat and quickly skim off any foam from the surface.
Step 7: Ladle the hot jelly into the prepared hot, sterilized jars, leaving 1/4 inch of headspace. Wipe the rims clean with a damp cloth, center the hot lids, and apply the screw bands finger-tight.
Step 8: Process the jars in a boiling water canner for 10 minutes (adjusting for altitude if necessary). After processing, turn off the heat, remove the canner lid, and let the jars stand in the hot water for 5 minutes before carefully removing them to a wire rack to cool completely, undisturbed, for 24 hours. Check seals; any unsealed jars should be refrigerated and consumed within a few weeks.