MoveIt 6 DOF arm: moving a box around a planar surface

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Hello ROS Users,

I have a 6 DOF robot arm. This robot arm is holding an object, say a cube.

Ultimately, I would like to specify an (x, y, z) position for the cube to reach on a planar surface, while ensuring the cube is perpendicular to the surface. I would like the cube to move around on this planar surface, for 2 scenarios.

1. Pick up the cube and reposition it such that the attached cube is flat against the planar surface
2. Once the attached cube is on the planar surface, slide the cube in a straight line

What would be the best way to do motion planning with MoveIt! for this 6 DOF robot arm with attached cube? I know how to do motion planning for reaching a specified target pose (position + orientation), but the orientation for the cube is problematic; I do not care what the yaw angle for the box ends up being (z-axis perpendicular to planar surface).

Edit: Was able to get an orientation constraint to finally work, took some time to figure out what quaternion and absolute axis tolerances should be set to. Is the orientation constraint only being satisfied for the final position in the trajectory? I am asking because the robot arm is doing a lot of strange maneuvers to reach the goal position, which is not what I am looking for. Also, some positions are not able to be planned to unless the robot arm is moved closer to the goal position.

Thanks