Right after the last episode of Breaking Bad, there was a live Talking Bad show episode with some of the actors and crew, where they told us that this was Jesse daydreaming of how he was crafting a wood box a long time ago in school, and how this daydream abruptly ends with the "leash" pulling on him like a captive dog.
On his group therapy Jesse talked about how he made this box for a class, and in the end he traded that box for some drugs. Note how the scene in the last episode suddenly changes from Jesse holding his box with a happy look on his face to him standing in the middle of a meth lab.
Penny Arcade Report's Ben Kuchera writes in his article which I suggest to read in full:
Jesse Pinkman is fantasizing about the creation of a beautiful wooden box, a call back to the third season where he discussed being inspired by his woodworking teacher. He traded the box he made in class for drugs, but this seems to be a vision of what might have been, a happy, healthy Jesse doing something that created an item of worth, something of lasting value, and taking pride in it.
You can say a lot of things about the act of cooking a near-perfect batch of crystal meth, but it’s an act of destruction. All those beautiful blue crystals will end up in the greater world, ruining the lives of the people who consume it. There is no satisfaction in a job well done once you understand that, and the fact that Jesse now dreams of creation is significant.
This is a quick interlude, and serves mainly to give us a peek into what Jesse wants right now. And he wants peace. Whether he ultimately gets it is open to interpretation.
In the last episode there are many moments that go way back in the show's timeline, reminding the viewers how things once were and how it all could've turned out differently.
Here's the youtube vid of that group therapy scene (s03e09).