4" 45 Degree Elbow. 26GA Black Stainless Single Wall Exhaust Elbow . Used inside, if chosen, over HT pipe to turn towards your exit hole. A Pipe adapter is used https://flameinnovation.com/product/4-ht-pipe-adapter/ to connect HT pipe to this elbow. Then, you use HT pipe to go through your exit hole. Cannot use single wall pipe to go through walls or ceilings. Clearance for combustibles on single wall pipe is normally 3" x the size of pipe you are using. A small article that talks about using single wall pipe. https://www.hearth.com/talk/threads/clearance-for-single-wall-pipe.157962/
Subsequently, if using this elbow, the seams need to be sealed. It is in how they are made to fit together. Making this angle on a machine isn't easy. So, it goes together a little different and sometimes the fit isn't the greatest. So, seal it around the seam. Likewise, predrill your holes too. For example, you can use a self drilling stainless screw. But, sometimes the tips burn off before you get it started. Much easier to drill. Secondly, trying to push too hard will leave a dent and a chance for an exhaust leak. In conclusion, 4" 45 Degree Elbow is a viable choice in some instances.
Burn your stove cool the first few times to season the bricks. Season the baffle board if it has one. Most Importantly, to season the paint.