Using a blender (or a large pitcher and an immersion blender - my preferred method) combine fresh squeezed lemon juice, sugar, and hot water. Blend until sugar has dissolved. Add fresh or frozen (thawed) strawberries and blend again till berries are well blended.
Add 3 c cold water, blend till combined. Pour through a fine mesh sieve if you wish to remove some of the strawberry seeds.
Refrigerate for at least an hour before serving.