Line two half sheet pans with parchment paper. Fill a piping bag fitted with a 1/2" plain tip (or you can snip the tip off a disposable piping bag) with the almond filling. Whisk 1 egg with a tablespoon of water for egg wash.
Turn the dough out onto a lightly floured surface. Roll the dough to a 15"x16” rectangle.
Use a pizza cutter or sharp knife to cut the dough into 3rds along the 15" side and 4ths along the 16" side. You should have twelve 5"x4" rectangles. Lightly brush all the squares with egg wash. Starting 1/2" from the edge of a rectangle pipe a 1/2" thick line of filling along the short side of the rectangle about 1/3 from the top. Stop a 1/2" from the other edge. Repeat with all the rectangles. (see photos)
Wrap the top side of the dough over the filling and set it just over the other side of the filling. Fold the bottom side of the dough up to meet the seam. Press the the seam and both ends to seal in the filling. You'll end up with a tube of filling wrapped in dough with a flap of unfilled pastry (see photos).
Place a pastry on the prepared baking sheet with the seam side down. Use the tip of a paring knife to cut 1/2" slits in the unfilled flap of dough (these are the "claws"). Bend the two ends of pastry back to form an arc and to open up the "claws" of the pastry. Repeat with all the pieces of dough. You should fit 6 pastries per sheet pan.
Cover the pans with plastic wrap and set aside to rise for 1 1/2 - 2 hours, or refrigerate overnight. (see note) The dough should look lighter and a little puffy but may not double in size. If you refrigerate the pastries allow them to come to room temperature before baking. While the dough is rising, preheat the oven to 375 °F.
Brush each pastry with egg wash and sprinkle with sliced almonds. Bake in the middle rack of the oven until the pastry is well-puffed and golden brown, about 15 minutes. Rotate the trays halfway through baking to promote even browning.
While the bear claws are baking, whisk 2-3 teaspoons milk and 1-2 drops almond extract into 2 oz confectioner sugar. The glaze should have the texture of pancake batter. Add more sugar if it’s too loose or more milk if it’s too thick.
Remove the bear claws from the oven and let them cool on the pans for 10 minutes. (See note) Use a fork or whisk to drizzle the glaze over the warm pastries.
Serve slightly warm or at room temperature.