We let them dry overnight then sealed them with Minwax Wipe-On Poly ($12). Note: you might want to let the stain sit a little while longer than we did because the Wipe-On Poly did remove some of the color (which worked out in our favor because then it was a closer match to our tv stand).
I would totally recommend buying a few bags of the rags (seen in the above photo). They are like $3 a bag at Lowe's and we used approximately 2.5 bags. If you want to save a few bucks, a cut-up t-shirt will work just as well--I wasn't able to convince my husband to sacrifice a shirt (or two) for the cause, so this was my only option.
The back of the can says to let the sealant dry for 24 hours before light use, so we patiently waited the allotted time before nailing it all together.
We then made an inset box for the middle of the table using leftover material (four sides and a top piece), and stained it to match. You would think this step would have been easy, but it was actually the biggest pain of the entire process! You could technically build the box into the unit itself, but we wanted the ability to remove it in the future (you never know when you will need a good hiding spot). In order to make this removable, we drilled two small holes into the top of the box--just large enough to use two small allen wrenches to pick it up.
Altogether, this coffee table project cost us about $175. A little pricey if you're looking for a "cheap" DIY project, but if you are looking for a quality coffee table it's very affordable! It took us roughly 3 days to make (including the dry time).
Update: We found the perfect baskets to fit inside the crates at Target for about $13 a piece:
If you like this DIY Project, be sure to pin it!