Preheat the oven to 425˚F (220˚C). Lightly grease a 12-inch cast-iron skillet or baking sheet with vegan butter or non-stick spray.
To make vegan buttermilk, mix together the almond milk and lemon juice in a glass and let sit for 5-10 minutes, until the mixture starts to curdle.
In a large bowl, mix together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt until just combined. Add in the cubed vegan butter and cut using a pastry cutter or even two forks until the butter chunks are pea-sized and the mixture is crumbly.
Pour the vegan buttermilk into the flour mixture and stir gently to combine.
On a clean and floured surface, use your hands to take out the dough from the bowl. Gently bring together the dough with lightly floured hands. Roll the dough into a rectangle about 9 x 13 inches. Fold the right side of the dough over the middle and then repeat with the left side (you are essentially folding the dough into thirds). Turn the dough horizontally and roll out again to 9 x 13 inches. Repeat the folding process and roll out one more time to 9 x 13 inches (dough should be about ½ inch thick). Use a biscuit cutter, glass, or even Mason jar to cut biscuits. You can combine the scraps and keep rolling out until you can’t get anymore biscuits. You may get 14-18 biscuits depending on their size.
Place biscuits close together in the greased skillet or baking sheet and bake at 425˚F (220˚C) for 13-15 minutes, until the tops of the biscuits turn golden brown.
Remove from the oven and let cool for 10 minutes before assembling.