Preheat oven to 350 degrees F (175 degrees C). Line a 10x15-inch jelly roll pan with aluminum foil; spray with cooking spray.
Arrange pecans in a single layer in a shallow pan.
Bake in the preheated oven, stirring halfway through, until pecans are toasted and fragrant, 10 to 12 minutes.
Arrange graham crackers in a single layer on the prepared jelly roll pan.
Combine brown sugar, butter, and cream in a heavy saucepan; bring to a boil, stirring occasionally, until sugar is dissolved, about 5 minutes.. Remove from heat and stir in vanilla extract. Fold in pecans. Pour pecan mixture over graham crackers, spreading to coat.
Bake in the preheated oven until topping is bubbling, 10 to 11 minutes. Remove from oven and immediately sprinkle with salt. Transfer coated crackers and aluminum foil to a wire rack to cool, about 30 minutes. Break into bars.
