For this example I created a very basic transform in 3 steps using the animation timeline.
Hint: A useful tool for editing the path is using a 3 viewport style, with a top down and side on view.
Clicking on the actor which the transformation has been carried out on will bring up, in the properties, an animation path style. Swapping this to custom brings up manipulator handles to change the path.
Using the manipulating handles the path can be adjusted to the need; a rotate transform in this case was then added to make the box turn around the corner.
The final result can be seen below.