Slow Cooker Peach Cobbler

INGREDIENTS

• 1/2 teaspoon freshly grated nutmeg
• 3 1/2 ounces rolled oats
• 1/2 teaspoon baking powder
• 20 ounces frozen peach slices
• 1/2 teaspoon freshly ground allspice
• 4 ounces all-purpose flour
• 6 ounces dark brown sugar
• 1/4 cup unsalted butter, at room temperature, plus extra for the cooker
• 1/4 teaspoon kosher salt