Add the lentils to a large bowl and gently mash them with a fork or your hands. I prefer to keep some pieces whole for texture.
Add in the oat flour, grated carrots, harissa, lemon zest, herbs and spices and combine together with your hands until everything is mixed well.
Shape the batter into burgers, you'll get about 5-6 depending on size. If it's sticky to work with, I suggest shaping them with wet hands.
Heat a skillet on medium/low heat, and add in about 1 tbsp of olive oil. Cook the burgers for about 5-6 minutes per side, until golden brown.
Prepare the tahini sauce by whisking or blending together the ingredients until smooth. Add more water if needed to thin out the sauce.
Serve the sauce over the burgers in a bun or a salad.
Leftover lentil burgers can be frozen for up to 2 months, or refrigerated for up to 5 days.