What will it be used for? Shaving legs? A place to put bath products? Regardless, I would suggest not building it into the shower but instead getting a freestanding teak bench or some think like that. Without knowing exactly how you plan to use it, my first thought was the back right hand corner, just beyond the door.

Mostly for aging in place. We are building for the future, for now probably leg shaving.

Then for sure buy a freestanding bench. So it can be moved under the shower head if that becomes necessary. But put in grab bars for sure - or at least blocking in the walls so they can be added later if/when necessary.

Agree with others not much room for a built in bench how you have it. Did a mock up drawing took out your linen closet. Made the shower a little narrower but longer and made the toilet closet wider. Moved the door closer to the shower. If you do a half wall with framless glass above it. You could do walk in shower without a door. If you wanted a built in bench could move the shower entrance down and put short shower wall near the end and do a built in bench and do a shower door. We have similar set up and really like it. The builder put the shower controls on the wall where we walk in opposite of the shower head.

It’s a 6’ shower. There’s plenty of room for a bench, or to make it meet ADA. But not with that weird angled entry. A trench drain across the back, and a shallow bench along the left side will be fine for now and still leave plenty of room to age in place.

Sophie would you recommend more like what GP each has done?

Yes what gpeach did is much better. However I'm in the camp that says just get a freestanding bench.

The freestanding benches can be stylish and (important!) stable. And if someone becomes disabled, you can change them out for one with grab handles if needed. And you can put them where you want them. And they aren't necessarily expensive.

Agree, don't forget about the grab bars.

And go ahead and enlarge the doorways a few inches. You won't see or feel the difference, but it might just make things easier one day.

We’ve got a 4’ x 6’ shower and going free standing so we can move it.

These are close to the size you're considering. I suggest barrier free. No need to cut into joists with today's products and as others suggested at a minimum install blocking for future grab bars.

@Creative Tile Eastern CT - Can you please mention what those products are that you can use to avoid cutting into the joists? Thanks...

There are several - ARC, VIM, USG etc. I prefer the USG as it is the most versatile with custom bases in 5 days. Others require you to cut base to size which means you are cutting into the slope. This leaves you with a dip in the floor where it meets the wall. They all will work but not all offer a complete system for hundreds less. Just one tile guys opinion. http://www.durockshowersystem.com/en/resources/installation-guide.html#barrier-free-install-barrier-free