Rigging technique for flexible cardboard packaging I am trying to mockup a packaging project of mine which looks something like this:
When the package is closed a little basket is enclosed by two outer cardboard flaps that come down to the sides when opened. The rigging of this fairly flexible outer part of the packaging is the issue at hand. Often packaging tutorials available online revolve around very easy &quot;boxy&quot; packages with flaps that are comparably easy to rig, e.g you just need to rotate a single bone to open and close a lid. Here the process to me appears harder. I have experimented but am not very happy with the outcomes. I am illustrating my approach below. I would be very happy about any feedback on how I could do things better or differently.
My strategy so far (also check the corresponding images


Create an armature with assigned vertex groups
inverse cinematics constraint on the upmost bone
Have some really small bones at the lower end of the flap so that it can bend more smoothly there (I found that as the paper folds at a very steep angle, without the small bones down there it would strongly distort the mesh)
Make bones bendy with three segments each
Later symmetrize the bones so both sides can be animated with the same movement for opening

Any help is greatly appreciated, so thanks in advance!
Here you can find the file in question: 
or here: https://liuonline-my.sharepoint.com/:u:/g/personal/jonfr654_student_liu_se/ETFOIt6rv-hCgdf29ISxs20BJmlOo-appmws9F2H0LyAgw?e=UqtCYg
I am unhappy with this setup for multiple reasons:

I am not able to symmetrize the bone structure so I can animate the identical movement on both side (when I symmetrize the bones they are duplicated and pasted at the same location instead of being mirrored by the axis)
The bending of the mesh by the bones seems to influence the surface structure (segmentized) , which you can see when you render. 
If you look at it from the side, you can see that the curve created by the bones is not smooth but rather bumpy. 
I feel I could have more control over the shape of the package. At the moment I'm just pulling around the upmost bone to somehow shape the armature to my satisfaction.

When using shade smooth I run into a problem: There seems to be an inner edge which is visible when selecting the object. Apparently blender is trying to shade smooth that edge, that should not be there
To make sure that the slot is sharp and to avoid unpleasant mesh folding, you need to rework the topology and bring a new bone that overlap the slot. Now parent With Automatic Weight again, give your object a Subdivision Surface modifier (with a Subdivision of 2), and right click and Shade Smooth:


The way you wanted to mirror your animation is not the right one, you need to create bones for the left part. Apply the rotation of your armature, create a root bone, change the name of your bones to bone1.R, bone2.R, etc, symmetrize your armature:

Delete the Armature modifier of your object, parent again, for example With Automatic Weight, switch to Weight Paint mode, set your brush correctly, give some corrections so that it works the way you want:


If you want the left bones to copy what happens to the other side, give them Copy Rotation constraints:

The blend file: