Preheat the oven to 350 degrees F (175 degrees C). Pour peaches and juice into a 9x13-inch baking dish.
Combine flour, sugar, and butter in a bowl; mix and knead with hands until crumbly. Sprinkle over the peaches, then scatter pecans over top.
Bake in the preheated oven until topping is golden brown and peaches are bubbly, 45 minutes to 1 hour.
