If you are small, agile, and strong its easy. I'm big, creaky and feeble, so this isn't my favourite task.
The rear seat squab has a red push catch visible to rellease it. Removing this gives access to the screws securing the seat back, which the pushes out upwards.
The lower sear belt fixing is one bolt, easy, but don't lose the spring that holds iit flat to the floor when not in use - and good luck refitting it.
The only real problem, however, is the inner window seal. This should clip to the top edge of the trim alongside the seat, but often these clips are broken or missing, in which case it may be glued to the trim. If this is the case, care is needed. If its really neatly done and looks good it is, just, possible to take the two out as one piece, but its awkward. If its a clumsy bodge then you need to cut the glue without cutting the trim.
There is a heavy trim on the door opening edge which just pulls free, and you may have a plastic pocket liner alongside the seat. Screws for this and the side panel are clearly visible.
Wiggle the side panel free and you're there.
Technically easy, but leave plenty of time.
Steve