Cut the watermelon into cubes and remove any seeds. You should have about 6 cups of cubed watermelon.

Place the watermelon cubes in a blender or food processor and blend until completely smooth. You should have about 4 cups of watermelon puree.

Pour the watermelon puree through a fine-mesh sieve or cheesecloth-lined colander to remove any pulp. Discard the pulp.

In a large bowl, whisk together the strained watermelon puree, heavy cream, whole milk, sugar, lemon juice, and salt. Whisk until the sugar is completely dissolved.

For Ice Cream Maker Method: Chill the mixture: Cover the bowl with plastic wrap and refrigerate for at least 4 hours, or preferably overnight.

For Ice Cream Maker Method: Pour the chilled watermelon mixture into your ice cream maker and churn according to the manufacturer's instructions. This usually takes about 20-30 minutes. The ice cream is ready when it has a soft-serve consistency.

For Ice Cream Maker Method: For a firmer ice cream, transfer the soft-serve ice cream to an airtight container and freeze for at least 2 hours before serving.

For No-Churn Method: Pour the watermelon mixture into a freezer-safe container. Place the container in the freezer for 1 hour. After 1 hour, remove the container from the freezer and use a fork to break up any ice crystals that have formed. Stir vigorously to redistribute the ice crystals. Repeat this process every 30 minutes for the next 2-3 hours.

For No-Churn Method: After the initial freezing and stirring process, cover the container and freeze for at least 4 hours, or preferably overnight, until the ice cream is completely frozen.

Let the ice cream sit at room temperature for 5-10 minutes before scooping. Scoop into bowls or cones and garnish with fresh mint leaves, if desired. Serve immediately and enjoy.