I use stash when I forget to branch. So I might be working and then realize I never branched. So I stash my changes, create a new branch, and then pop my changes on the new branch.
There's nothing wrong with your workflow, btw, stash works in that case, as long as you immediately pop & don't get interrupted by lunch or a phone call.
Stashing is obviously providing some value that people like, it's very popular. But considering that it has extra danger, and that it's really easy to work without stash, I'm still confused why it's so popular.
And fwiw, most of the stash accidents I've seen are fairly simple scenarios like you described, and some teeny tiny twist or interruption causes someone to get confused and lose their stash, or think they lost their stash, and panic.
So in this case git stash works a lot better for a 'temporary' commit, kind of deal.
It might not be optimal but I've found the process to work pretty well for this particular project's situation.
Also works well for this use case
In this case, simply create the branch and switch to it (git checkout -b branchname) and you're good. It's like it never happened ;) (remember that branches are just labels - until you commit it doesn't really matter).
legit: https://github.com/kennethreitz/legit [1]
[Ignore the pretentious "for humans" tagline though...]
This isn't completely safe because deleting a branch also deletes its reflogs, but it does avoid use of the stash command at all, which I find good for my own safety (because it reduces cognitive load). And it scales obviously to making multiple commits onto the temporary branch, etc.