Slice tops from strawberries, discard. Add strawberries, agave, and lemon juice to a blender and pulse until strawberries are liquid. Strain juice through a sieve if you prefer most of the pulp be removed.
Pour the juice into a 1/2 gallon pitcher, add slices of lemon, fill with chilled water. Don't overfill pitcher with water, add just enough to make 1/2 gallon. Pour over ice and enjoy!
Garnish sides of glasses with a lemon slice and half of a strawberry. Also, try adding a few sliced strawberries to the pitcher. This is such a pretty drink.