In a medium saucepan, bring sugar and water to a boil. Remove from heat and let cool to room temperature.
Place strawberries into a food processor or blender and blend until smooth to make strawberry puree.
Pour strawberry puree into the sugar water. Add lemon juice. Stir well.
Pour strawberry lemon mixture and cold water into a large pitcher. Stir well and add ice. Pour into glasses and top with chopped strawberries and a lemon slice.
Notes
Make ahead. Make the lemonade but leave out the ice cubes. Store in the refrigerator until ready to serve. Add ice to the pitcher or pour over ice in individual glasses.
Store. Store any leftover strawberry lemonade in a covered pitcher or jar in the refrigerator for 7-10 days.