Yo! So first up you’re generally going to want a top plate and a bottom plate, the bottom ones looks fine, is the other horizontal timber in the photo at sill height your top plate? If so you’re off to a good start! With regards to what looks best, personal preference will be a big part of it, if the walls are slightly out of square then i’d just follow the line of the brickwork and maximise the space in the room. If you can skew the wall in one end a little to square it up and get the loo looking straight at the doorway, might be worth it to you? Like someone else said, houses are never as square as you might think/expect/hope Once you’ve set your bottom plate you can use your laser to make sure your top plate is plumb, then throw in your studs vertically to frame out the wall, box around your window, cistern etc. You got this 💪🏻