Place dates in a bowl filled with warm water. Let stand 1 hour.
Preheat oven to 375°F. Line a large baking sheet with parchment paper.
Combine sugar, oil, and vanilla in the bowl of an electric mixer; beat on medium speed for 1 minute. Turn mixture to medium-low and gradually add flour, stopping to scrape down sides as needed, until incorporated. Continue on medium-low speed and add 1/2 tsp. of the salt, and cashew milk in 1 Tbsp. increments until mixture starts to come together as dough. Turn off mixer and shape mixture into a ball of dough, pressing any loose bits into dough; remove from mixer.
Place coconut flakes in a small bowl. Carefully roll dough mixture into 15 or 16 uniform balls. Roll balls in coconut flakes and place on prepared baking sheet. Using your index finger or thumb, press a thumbprint into the center of each ball, about 1/2-inch deep (if edges of cookie start to break, simple press back together).
Bake cookies at 375°F for 10 minutes. Remove from oven and gently press thumb back into indentation. Allow to cool for 10 minutes.
Drain dates and place in a mini food processor or blender with remaining 1/4 tsp. salt. Blend for 2 minutes, gradually adding warm water in 1 Tbsp. increments until dates become smooth and jammy (about 3 to 5 Tbsp. water total.) Fill each thumbprint indentation with salted caramel date mixture. Sprinkle flaky salt overtop.