Hall the watermelon chunks into the blender, ensuring they are uniformly cut for smooth blending.
Add the salt and lemon juice to the blender with the watermelon. Secure the lid and blend on high until the mixture is completely smooth and vibrant red, about 30 seconds.
Pour the blended mixture into a shallow baking dish or tray, spreading it out evenly with a spatula for quick freezing.
Place the tray in the freezer and let freeze for at least 4 hours, checking occasionally. Use a fork to scrape the icy surface every 30 minutes during the first 2 hours to create flaky, crystalline layers.
Once fully frozen and scraped into icy flakes, serve immediately in chilled bowls or glasses, garnished with small watermelon wedges if desired.
