Preheat oven to 350°F. Line a 9 x 13 pan with foil or parchment, and spray with non-stick spray.
Using a hand mixer or stand mixer fitted with the paddle attachment, combine granulated sugar, baking powder, flour, and salt. Add butter, egg, vanilla, and almond extract.
Beat on low speed until the butter is evenly distributed in small pieces and the mixture is crumbly.
Pour a little more than half of the mixture into the bottom of the prepared pan. Use your hand or the bottom of a measuring cup to evenly press the dough into the pan. Stir sliced almonds into the reserved mixture (for topping).
Gently stir together all ingredients until combined.
Spread the peaches evenly over the crust, then crumble the reserved dough over the top of peaches. Bake for 40 minutes until top is golden brown.
Combine the ingredients in a pot, whisk together and bring to a boil. Cook for 3-5 minutes until the glaze thickens. Remove from heat, let cool and drizzle over the slice.