Prepare your juicer. You can also blend and then strain through a fine-mesh strainer afterward, it will just be a bit more work.
Slice your watermelon into quarters and use a knife to carve out the red flesh and chop into pieces that fit your juicer, and juice. In this recipe, a mini watermelon produced 2 1/2 cups of juice.
Slice your Meyer lemons into halves or quarters and juice. In this recipe, two Meyer lemons produced a 3/4 cup of juice.
