It has been discussed extensively in the thread. There is no easy way of making a waffle fry at home, at least not with consistent quality. The primary issue is the blade design. I tried several mandolins from $8 to $200+, as well as couple manual tools, with no luck. The core waffle fry design contains 3 features:
1. Cross-cut (horizontal one side, vertical the flip side)
2. Thick
3. Holes
Here is a sample image:
http://static4.businessinsider.com/...keting-power-of-chick-fil-as-waffle-fries.jpg
A mandolin can cut holes, but it's very thin, like a potato chip. A mandolin can also cut thick fries, but then you lose the holes. Waffle fries without holes does not offer the same eating experience as waffle fries with holes (we're getting real technical here, haha). Due to the nature of the blade design on the 5+ mandolins I tried, you can't achieve a thick cut with holes like a traditional waffle fry.
I think they either have a special press or some kind of custom slicing machine that (1) has deep grooves to allow for cross-cut holes & a thick slice, and (2) allows for consistent. The best results I've gotten have been with the hand tool I bought, but it's extremely difficult to get consistent quality by hand because there's no jig to line it up perfectly every time, so you end up not getting holes in the final product for the majority of the slices.