In a blender puree strawberries. Strain puree through a sieve to remove seeds. Set strained puree aside.
In a small saucepan combine water and sugar. Over medium heat dissolve sugar in water (simple syrup). In a one gallon container, place simple syrup, and stir, making sure sugar dissolved. Add lemon juice, strawberry puree, and water to render one gallon. Stir well until well mixed. Pour strawberry lemonade over a glass of ice and garnish glasses with lemon slice.