Place the third/final cake upside down on top of the frosting, so that the flat bottom of the cake faces upwards. Gently press and apply a thin layer of frosting on top of the third cake. Using a spatula, level the top and the oozed out frosting around the sides of the cake to form a thin and evenly covered crumb coating.
Refrigerate 30 minutes for the crumb coating to set properly.
Now apply the final coat of frosting on top and around the cake, starting from the bottom to the top. Scrape down the excess frosting using a scraper. Refrigerate for another 30 minutes before pouring the matcha drip.