Combine the almond milk (2 and 1/2 cups), locust bean gum, xanthan gum, and agar in a medium saucepan. If you want to make a sweetened yogurt, also add the maple syrup and vanilla seeds. Heat over medium heat until it reaches 185°F (85°C), whisking constantly to make sure all the gums are fully dissolved and don't stay at the bottom. Remove from heat at soon as it reaches 185°F, just before it boils. Transfer to a large glass bowl and let sit for about 20 minutes, or until the temperature reaches 110°F (43°c). This is important, if the milk is too hot it will kill the cultures. Using a thermometer is strongly recommended.
Once the milk is at the right temperature, stir in the yogurt starter. At this step, the almond milk will have already thickened and may appear gelatinous, don't worry this is totally normal. Give it a good whisk to break any "lumps", and make it fully smooth again. Pour into glass jars and close the lid, or use plastic wrap to cover.
Place the jars in a baking dish filled with warm water, they should be half immersed. If you have a yogurt maker, skip this step and just put the jars into your machine.
Place the baking dish with the jars in a 105°F preheated oven for 6-10 hours depending on how sour you like your yogurts. Personally, I prefer them with a milder flavor so I let them culture for only 6 hours.
Transfer the yogurts to the refrigerator and let cool for at least 8 hours.
Enjoy for breakfast or dessert, sweetened with some maple syrup and topped with granola, fresh fruits, jam or nut butter. Always give the yogurts a good stir before eating!
The yogurts will keep for up to 4 days in the refrigerator.