Preheat oven to 375°F (190°C).

In an 11x8-inch glass baking dish, toss together strawberries and sugar until combined. Spread in a single layer.

Bake until very soft, dark in color, and fragrant, 30 to 45 minutes, using a spatula to carefully stir every 10 minutes. Strain in a fine-mesh sieve, pressing on solids, to collect juice. Let berries cool enough to handle, and chop. Reserve chopped berries and juice.