I used to do a lot of interviews for front-end engineers. The process I settled on was to give them the following setup:
- some mock-ups from when we first designed our product gallery
- a json file that listed the products names, pictures, description, etc.
- a blank css file
- a html file that loaded the css and jQuery, and then made an ajax request to load the json file. (This was back when jQuery was pretty much state of the art for front-end.)
With all of that in place, I'd explain that I'd like them to work on building a product gallery that looked similar to the mockups. I would further explain that, since we only had an hour, I didn't expect a polished or even fully functional product, but I'd just like them to dive in and see how far they got. They could use their editor of choice and ask any questions they wanted.
I felt like this gave better insight to candidates skill and workflow. My colleagues all gave more traditional interviews, so I also felt like there was a good counterbalance if someone didn't do well with this kind of interview.