Slice bananas into 1/4" thick slices. Line your pie crust with banana slices. Set aside.
Heat flour, sugar, and salt over medium heat. Slowly stir in milk. Cook until the mixture becomes bubbly and foamy.
Mix in egg yolks. Stir continuously and bring the mixture to boil.
Mix in melted butter and vanilla extract. Stir until well combined. Remove from heat and cool mixture for 10 minutes.
Pour mixture into pie crust. Place pie on a metal rack to cool for 30 minutes, then cool in the fridge for 1 hour or until you're ready to serve the pie.
Top slices of pie with whipped topping and banana slices! Serve cool.