Place cut strawberries, watermelon, and sugar in a bowl and toss well. Cover and freeze overnight. Remove from freezer and set on counter 5 to 10 minutes before blending so all the sugars and flavors can mesh together. When ready to blend place fruit mixture, almond milk, honey, and milled flaxseeds in blender and blend on high for 2 minutes, then blend on "whip" cycle for 2 minutes for a nice light and fluffy smoothy. Enjoy immediately.
If you are in a rush then skip the freezer but let the fruit sit in the sugar for as long as you can wait before blending.