Hull and quarter 1 pound of the strawberries; combine in a medium bowl with sugar and lemon juice. Set aside, stirring occasionally, about 10 minutes. Place 1 cup cold water in a small saucepan; sprinkle gelatin over water. Let stand at least 5 minutes to soften.
Working in batches, puree strawberry mixture in a blender. Strain through a fine-mesh sieve into a large measuring cup after each batch (discard solids). Add enough water to strained juice to measure a total of 3 cups liquid. Set aside.
Heat softened gelatin over medium-high, just until it begins to bubble around the edges and gelatin has dissolved (do not boil), 2 to 3 minutes; stir into strawberry juice. Divide mixture among four serving glasses. Chill until firm, 3 to 4 hours.
To serve, hull and dice remaining 1/2 pound strawberries; spoon on top of chilled gelatins.