Wide flat boots

and let me clarify, when I say wide and flat, I mean I literally have the foot profile of a rectangle.

Any wide boot that I can think of is also high volume. If you really have a low volume but wide foot, then you need to fit to the volume/instep/heel and the make the shell wider where you need it. Pick the boot that has the correct instep & heel fit you are looking for, then have your boot-fitter go to town on the forefoot, toe box, and length.

My suggestion and strategy: Don't let people over the internet fill your head with ideas on boots that are going to work best for you without seeing/measuring your foot. When buying new boots - go to several shops with a super open mind and have them all fit you. This process takes 20-30 minutes, so for a $500 investment I don't feel too bad about taking up 3 fitter's time. Get several opinions on what boot shell best fits your feet, and really ask them "what shell best fits my foot?" and take into account which is the most comfortable in the moment. The shell is the main detail that really has to get nailed to save a ton of trouble down the road. With the proper shell selected, fitters can usually pull out an arsenal of tricks to eliminate problem areas. If possible, I highly recommend purchasing your boots at the store closest to where you ski most frequently. This way, you can come back if you're still having issues and hopefully work with the tech who knows your story. If you believe you've found the proper shell and seen several fitters already, another suggestion is to basically watch all of Patriot footbed's YouTube videos and learn as much as you can about ski boots. They may be cheesy but I promise it is well worth the time and you'll probably pick up on some tricks that might help your exact situation: https://www.youtube.com/playlist?list=PLM7W94B6e4-2-Ekxe9pWxIe3JoQu94VVg . From your description of a wide flat foot, if you've already got a footbed and are still having weird volume issues (say your foot is truly flat), a volume reducer might be of assistance: https://patriotfootbeds.com/products/volume-reducer check out some of their other after-market products if you really want to try and save your current boots. Sometimes $50 in upgrades can save you from buying brand new boots. Final thought, for everything but boots, style over function. For boots, if a fitter puts you in rainbow camoflauge tie dyed boots, you wear those proud with the knowledge that your feet will finally stop hurting. Hope these thoughts help!