In a bowl, combine the beans with 900ml water and 1 teaspoon of the salt. Let soak for 10 to 12 hours, or overnight. Drain the beans and set aside.
Select the Sauté setting on the Instant Pot, add the oil and garlic, and heat for 2 minutes, until the garlic is bubbling but not browned. Add the onion and sauté for 5 minutes, until the onion is softened, and the garlic is toasty and brown. Stir in the stock and use a wooden spoon to deglaze the bottom of the pot.
Stir in the carrots, spices, and beans, making sure all the beans are submerged in the cooking liquid.
Secure the lid and press the Cancel button to reset the cooking program. Select Pressure Cook, or Bean/Chili setting and set the cooking time for 30 minutes at High pressure. (The pot will take about 15 minutes to come up to pressure before the cooking program begins.)
When the cooking program ends, let the pressure release naturally (this will take about 40 minutes). Open the pot and stir in the tomato paste and lemon juice. Taste and adjust the seasoning with salt, if needed.
Ladle the tagine into bowls. Drizzle with oil and sprinkle with mint.
Serve hot, with couscous or flatbread.