Allow squash to rest for 5 minutes after cutting to release its moisture. Stir the flour, sugar, and salt together in a shallow bowl. Dredge the squash slices in the flour mixture, shaking off any excess, and set aside until needed.
Melt the shortening in a large skillet over medium-high heat. Arrange the squash in a single layer in the skillet. Cook, turning once, until golden brown, about 5 minutes. Drain on paper towels.
