General advise to apply a morphTarget

I’m a bit confused about what the best/easiest option is to have a mesh of a GLTF model morph from a planegeometry back to it’s original shape.

I’m struggling with understanding how I can create a ‘morpTargetDictionary’ so that the mesh of the GLTF model ‘knows’ that it needs to morph from the planegeometry back to its original state.

Or would be the better/easier option to create this within Blender using shapekeys?

Any advise is very welcome as I’m a bit stuck.