Usui Sensei's training hall (dojo) was of medium size.  His dojo in the Aoyama district of Tokyo was a 12 mat dojo.  Tatami mats are roughly 3 feet by 6 feet so the size of the room would have been something like 12 feet by 18 feet.   The room was either attached to Sensei's dwelling or was a space he rented in another building. 

Before entering the dojo there was a simple place for the Shinto misogi practice of temizu -  the cleansing of the hands and mouth using a dipper and water from a container. 

The dipper was picked up in the right hand (at the end of the handle) and filled with water from the fountain or bowl; one quarter of the water was poured over the left hand for ritual cleansing - this was done away from the fountain or bowl; then the now cleansed left hand held the dipper in an area not touched by the right hand as this was now "unclean"; another quarter of the water was poured over the right hand to cleanse it; the right hand now held the dipper in the middle of the handle and poured another quarter of the water into the left hand from which the mouth was rinsed;  The final quarter of water was upended so that it flowed down the handle of the dipper, thus cleansing the complete handle for the next person. The dipper was then placed over the bowl, cup facing downwards.

In 1925, Dr. Hayashi introduced the process called Kenyoku-ho into the dojo.  It was another form of cleansing that could be done inside the dojo in order to disconnect oneself from a previous exercise or act.  The 3 part inner brushing and the 3 part outer brushing were intended to represent a form of temizu, cleansing the inner and outer you. 

Next, before entering the dojo you would remove your shoes and leave them outside before entering the dojo. 
 

shin bow

Once inside the dojo, the doka (student) would give a shin bow towards the tokonoma and then the same to Usui Sensei.  If there were other doka present then a gyo bow would be exchanged with the group.  Those already present would move off their zabuton (floor cushion) and give a gyo bow as well, before returning to their cushion.

gyo bow

Note that the bowing might also be done while standing. The politeness of bowing was also executed between doka when they were given a kata exercise to practice. Each time they would get off their zabuton and gyo bow to their partner before and after the exercise. When class was over, students would again shin bow to Sensei and to the Tokonoma before leaving the dojo.

The tokonoma is a small alcove in the wall that faces opposite the entry way of the room. It holds a kakejiku (hanging scroll) and in the case of the Usui dojo, this was the original Gainen. In a typical Reiki dojo tokonoma after the passing of Sensei, you might also find a picture of Sensei.  This might be a copy of the large portrait photo that Dr. Hayashi had taken before Sensei's passing.

Doka were seated in seiza style on their zabuton. They were in pairs of rows running from the front of the dojo to the back.  There were up to 4 doka in a row and each pair of rows faced each other. The doka opposite you would be your partner for any exercises.  In the smaller dojo there were sometimes 2 sets of rows (thus 4 lines of doka). The senior doka would sit closest to the front of the dojo.  Sensei would sit at the front of the class and teach from there.  At the end of class he would also sit quietly as all students filed out.

In 1923 Sensei moved the dojo to a larger premise in the Nakano district which at the time was outside the city. The dojo was now about twice the size as before and there was an additional room where Sensei would often sleep.  It would have been a long walk back to his Aoyama home, assuming his family still lived in this location.  Note that the Aoyama district is adjacent to the Shinano Machi district where Dr. Hayashi lived.