Preheat the oven to 175 C/350 F. Line an 8 inch cake tin with parchment paper and grease thoroughly with butter.
In a bowl, add the almond flour, sweetener and salt and give it all a goooooood mix. Stir the melted butter into the flour and mix till it comes together like dough. Press the almond flour mix into the cake tin and level it using your fingers, or a spoon, or, anything, really. Bake the base for 10 minutes, then take it out and leave it to cool.