Combine sugar, cornstarch, flour, and salt in a pot; whisk in milk. Heat to boiling. Whisking continually, boil for 1 minute.
Mix 1/2 cup of hot mixture into egg yolks; add mixture back into pot. Whisking continuously, cook over low heat until thick. Remove pot from heat and mix in vanilla, cinnamon, and nutmeg. Let cool to room temperature, stirring often. Chill 1 to 2 hours.
Reserve 4 to 6 strawberry slices. Cut 1 to 1 1/2 bananas and lay in crust with the rest of the strawberries. Pour custard on top and chill 4 to 6 hours. Top with the rest of the sliced bananas and strawberries.