I think this goes without saying, but just in case: none of these will contain information necessary to follow the main story of the novels (if they did, they'd be part of the novels). But they allow me to build out the world a little more and incorporate a few ideas that didn't fit in the books.
The first two stories are now up. Both are intended to be read after the second book in the series, A Tide of Ice, though either can be read out of order or even as stand-alones.
The Truthspeaker is a short piece I originally wrote to get a better feel for setting and voice in A Tide of Ice. It's something of a prequel to most of the book, and it would work read before, after, or even as a standalone. I'm still suggesting you wait until after, but take that as a light recommendation.
The same is true of A Meeting in the Desert: this doesn't feature any characters appearing in the novels, and shouldn't spoil any plot points (though it may change your perspective on a minor piece of one character's backstory).