Preheat oven to 400°F/204°C and line a baking sheet with parchment paper.
Lay out 4 pieces of bread on the parchment paper.
In a food processor, make the Matcha Almond Frangipane: add in the ground almond, egg, sugar, butter, flour, matcha, almond extract, and salt. Blitz until the mixture is smooth.
Make the Almond Simple Syrup:
In a small saucepan, add the water and sugar.
Bring to a boil and stir occasionally to dissolve the sugar. Add in ½ teaspoon almond extract. Remove from heat and let cool.
Assemble:
Using a pastry brush, dab the almond simple syrup on both sides of each slice of bread, ensuring it is saturated.
Divide the matcha almond frangipane into 4. Evenly distribute the matcha frangipane over the 4 slices of bread. Use an offset spatula to smooth over the tops. Sprinkle the tops with flaked almonds.
Bake at 400°F/204°C for 13-15 minutes, until lightly golden. Remove from oven and let cool on a rack.
Dust with powdered sugar. Serve Matcha almond bostock at room temperature.