Prepare seven (8-ounce) canning jars and bring a large pot of water to a boil.
In an extra-large high-sided skillet, combine the strawberries, lemon juice and salt.
Zest the orange directly into the skillet, then juice the orange and add it to the skillet as well, removing any pits as necessary. It should be about ⅓ cup worth of juice.
Add the pectin, sprinkling it a little bit at a time, evenly over the strawberry mixture, and whisking in between each addition to limit clumping, until it’s well combined.
Bring the mixture to a steady boil over medium-high heat, scraping down the sides to keep the pan clean and stirring often with a heat-resistant spatula.
Add the sugar in one addition and stir to incorporate, using the spatula to break up any lumps.
Cook, stirring constantly and continuing to scrape down the sides of the skillet, until the mixture returns to a steady boil, then cook, continuing to stir constantly, controlling the heat, as needed, so it doesn’t boil over, for one minute more.
Once the preserves settle, using a large spoon, carefully but quickly, skim any foam off the top and discard.
Using a ladle, quickly but carefully transfer to the prepared jars, leaving a ¼-inch of headspace.
Using a paper towel, wipe the rims of the jar, to ensure they are clean and bone dry.
Place the lids onto the jar and secure with the screw the cap, twisting just until resistant. Have a clean linen dish towel on hand to hold onto the sides of the jars as they’ll be very hot.
Using a canning jar lifter (or a heavy-duty spatula with rubber ends), carefully place the jars into the boiling water and process for 10 minutes. The water should cover the jars by at least 1-inch.
Carefully remove the jars, placing them onto a cooling rack and let cool for at least 6 hours.
Check the seal. Any jars that have not fully sealed can be stored in the fridge for up to 2 months and fully sealed jars can be stored in a cool, dark place for up to 2 years.
