"Sorry, you lost me there..."Â Â
Let's start with your current configuration. Imagine looking down on your room from above, so that it looks like a square (almost).  The speakers are at the top of the square, with the bay window on one side, and the listening position is at the bottom of the square. Â
Now leave speakers and listening position where they are, and rotate the room itself 45 degrees (so that it is now a diamond instead of a square). Instead of there being a wall behind your listening position, now there is a corner. Likewise there is a corner between and behind the speakers. In practice you may have to scoot your speakers and/or listening position a bit closer to the center of the room for everything to fit.Â
Now that I think about it, it would probably make sense for the bay window to be along one of the walls beside the speakers, with some skewing of the diagonal (like 40 degrees of rotation instead of 45) if the bay window intrudes too much. Â
You might want to draw this configuration, and then take a ruler and trace the first reflection paths, with angle of incidence equaling angle of reflection. There will be a first reflection zone on each of the walls to the sides of the listening area.   I suggest diffusion or thick absorption in those areas, but if you use absorption, don't make the panels much bigger than they need to be to spot-treat that first reflection, at least at first, as imo too much absorption can suck the life out of the sound.  In practice you can find these first reflection zones by placing a mirror on the wall and moving it until you can turn your head and see the tweeter from your listening position.
I'm not sure it would be practical to place acoustic treatment panels along the bay window, and that's why I reconsidered where the bay window should end up. Â
Duke
Let's start with your current configuration. Imagine looking down on your room from above, so that it looks like a square (almost).  The speakers are at the top of the square, with the bay window on one side, and the listening position is at the bottom of the square. Â
Now leave speakers and listening position where they are, and rotate the room itself 45 degrees (so that it is now a diamond instead of a square). Instead of there being a wall behind your listening position, now there is a corner. Likewise there is a corner between and behind the speakers. In practice you may have to scoot your speakers and/or listening position a bit closer to the center of the room for everything to fit.Â
Now that I think about it, it would probably make sense for the bay window to be along one of the walls beside the speakers, with some skewing of the diagonal (like 40 degrees of rotation instead of 45) if the bay window intrudes too much. Â
You might want to draw this configuration, and then take a ruler and trace the first reflection paths, with angle of incidence equaling angle of reflection. There will be a first reflection zone on each of the walls to the sides of the listening area.   I suggest diffusion or thick absorption in those areas, but if you use absorption, don't make the panels much bigger than they need to be to spot-treat that first reflection, at least at first, as imo too much absorption can suck the life out of the sound.  In practice you can find these first reflection zones by placing a mirror on the wall and moving it until you can turn your head and see the tweeter from your listening position.
I'm not sure it would be practical to place acoustic treatment panels along the bay window, and that's why I reconsidered where the bay window should end up. Â
Duke