If this is the only toilet in your home, you can speed up the process a bit. You can use the speedset (link below), and after 30 minutes to 1 h from installing the tiles, you can walk on them, but it is quite a difficult material to work with if you have no experience, because it dries very quickly.
The second method is to use a normal thinset, but mix it quite densely (remember about remixing it after 10 min), then after about 4-6 hours, put the cardboard boxes on the tiles and install the toilet. The next day or the same day later, without removing the toilet, make grout and put the cartons on the tiles again.
Don't forget to apply glue/thinset to the tiles as well