In Rogue One: A Star Wars Story, Chirrut Îmwe and Jyn Erso have a conversation where they explain that kyber crystals power a lightsaber.
Chirrut: What do you know of kyber crystals?
Jyn: My father, he said they powered the Jedi lightsabers.
The parody video “How Rogue One Should Have Ended” has a scene where Chirrut Îmwe reveals that he made use of Jyn’s kyber crystal:
Chirrut: I’m one with the Force, and the Force is with me. And now…I have a lightsaber!
Baze: What the…?! Where did that come from?
Chirrut: Jyn let me borrow her kyber crystal. So I made my staff a lightsaber.
Chirrut: Don’t worry about it! I’m a Jedi now and that’s all there is to it!
While pretty funny, How it Should Have Ended does have a habit of ignoring things for the sake of comedy (and as they handwave here, he didn’t really have any time when he could have made it).
Still I’m wondering: could Chirrut Îmwe have possibly constructed a lightsaber out of Jyn’s kyber crystal if given the time?