Strawberry-Rhubarb Slab Pie

INGREDIENTS

• 5 cups all-purpose flour (spooned and leveled), plus more for rolling
• 2 tablespoons granulated sugar
• 1 teaspoon fine salt
• 2 cups (4 sticks) cold unsalted butter, cut into 1/2-inch pieces
• 1 cup ice water
• 2 pounds strawberries, hulled and halved (6 cups)
• 2 pounds rhubarb, cut into 3/4-inch pieces (6 cups)
• 3/4 cup granulated sugar
• 1/3 cup packed light-brown sugar
• 1/3 cup quick-cooking tapioca
• 1 1/2 packed teaspoons grated orange zest, plus 2 tablespoons orange juice
• 2 large egg yolks, lightly beaten with 2 teaspoons water
• 1/3 to 1/2 cup sanding sugar (optional)