Preheat the oven to 180C/350F and prepare a baking tray with baking paper.
In a high speed blender or food processor, blend the lentils, flaxseeds, salt, garlic and bicarb until puréed.
While blending, pour in the vinegar and blend until just combined.
Use a non-stick spatula to spread the mixture onto the baking paper into the shape of a pizza base.
Bake for 20 minutes.
Remove from oven and if the top has puffed up, carefully press it down using a spatula or other utensil.
Top with your desired sauce and toppings - optionally bake for a further few minutes to cook toppings, or serve straight away.