• Start from RUmRUvLUmLUv
• Flatten into a 3x2 rectangle with two stacks of two tiles in the central row
• Position it such that the higher tiles of the two stacks are flaps that can be rotated about their south side
• Actually rotate 90 degrees the eastern flap (in an upright position)
• Rotate 90 degrees a pair of adjacent tiles about their east side (valley fold) into the final shape

Also, this is hinge equivalent to RRUvRUmLmULv