To ensure that homemade vegan biscuits rise, use fresh leavening agents like baking powder and baking soda, and make sure the dough is cold before baking. Additionally, handle the biscuit dough gently and avoid overworking it. Bake the biscuits in a preheated oven, and don't forget to brush the tops with melted vegan butter or non-dairy milk for an extra lift and golden color.