I have previously written of my attempts to steam baguettes in a home oven. Steam produces nice “ears” and a glossy, caramelized crust similar to what you’d get from a professional bakery. You can closely replicate the effect for batards and rounds by baking in the controlled environment of a dutch oven, which traps the moisture in the dough until you remove the lid at 20 minutes or so. But it’s a challenge to do the same with baguettes.
Recently I’ve made some progress, using an inexpensive hack purchased on Amazon. It’s a “Nordic Ware Commercial High-Sided Sheet Cake Pan” whose interior dimension at the widest point purports to be just a little bigger than the outside edge of my half sheet pans. As usual, dimensions are approximate on Amazon but it does provide a tiny bit of overlap giving you a steam seal if you manipulate carefully before closing the oven. (Don’t burn yourself! I preheat my sheet pan but definitely not this cover, which I will want to position with unguarded fingers.)
As a bonus, the pan has a lid (which you can see in Amazon’s washed out photo above) so you can use it for baking giant half-sheet cakes, decorating in the pan, and then bringing to a picnic or some such. At under $18, there’s really no reason not to check out one of these guys.