Make the crust: Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, allowing overhang on two sides. Mix together almond flour, almond butter, ground flax meal, sugar, salt, and water until a crumbly dough forms. Press firmly into prepared pan. Bake for 15 minutes. Cool completely.
Cook sweet potatoes: Peel and cut sweet potatoes into 1½-inch chunks. Place in a pot, cover with water, and bring to a boil. Reduce heat and simmer for 15 minutes until tender. Drain well.
Prepare agar mixture: In a small saucepan, combine coconut milk, agar powder, and agave. Simmer while stirring frequently until agar completely dissolves, about 3-5 minutes.
Blend filling: Add drained sweet potatoes to a high-speed blender. Pour in the coconut-agar mixture, vanilla, and salt. Blend until completely smooth and thick.
Assemble: Pour filling over cooled crust and spread into an even layer. Cool at room temperature for 20-30 minutes, then refrigerate for at least 4 hours until firm.
Slice and serve: Use a sharp, clean knife to cut into 12 bars. Wipe knife between cuts for clean slices.