Use a citrus juicer and juice your lemon, set aside. Now take a high speed blender and take your defrosted frozen strawberries or fresh and blend them with a half cup water until totally smooth. The high speed blender should take the seeds and blend them, so you don't need to strain it.

Take a pitcher and add your lemon juice, the additional 3 cups of water, blended strawberries, and sugar. Stir until the sugar has dissolved. Let chill in the fridge until cold, stir before serving.