In preparation for the assembly, the kohanim walked through Jerusalem blowing trumpets to gather everyone to the Temple Mount. A large wooden platform was erected in the middle of the women’s courtyard. The king ascended and sat there so that everyone could hear and see him as he read (MT, op. cit. 3:4). If he wanted to honor the Torah by standing up during the reading, this was deemed praiseworthy. (See Tosafot on Sota 41a, s.v. “mitzva.”)
To honor the Torah and the king, the people assembled would pass the Torah scroll from person to person until it reached the king. The attendant of the synagogue on the Temple Mount took the scroll and gave it to the head of the synagogue, who passed it to the Deputy Kohen Gadol, who gave it to the Kohen Gadol, who passed it to the king. The king accepted the Torah scroll while standing (Sota 41a; MT, op. cit. 3:4).
Before and after the reading, the king recited the berakhot that are normally said at the beginning and end of an aliya. Afterward, he added seven more berakhot: 1) Retzei (Birkat Ha-avoda, from the regular Amida); 2) Modim (Birkat Ha-hoda’a, also from the regular Amida); 3) Ata Veḥartanu (the fourth berakha of the Yom Tov Amida); 4) a prayer for the Temple to endure, concluding with “Barukh ata Hashem, ha-shokhen be-Tziyon” (“Blessed are You, Lord, Who dwells in Zion”); 5) a prayer for the monarchy of Israel to endure, concluding with “Barukh ata Hashem, ha-boḥer be-Yisrael” (“Blessed are You, Lord, Who chooses Israel”); 6) a prayer for the service of the kohanim to find favor with God, concluding with “Barukh ata Hashem, mekadesh ha-kohanim” (“Blessed are You, Lord, Who sanctifies the kohanim”); 7) an extensive, unscripted prayer, concluding with “Hosha Hashem et amkha Yisrael, she-amkha tzerikhin lehivashe’a” (“Lord, save Your people, Israel, for your people needs salvation”), followed by “Barukh ata Hashem, shome’a tefilla” (“Blessed are You, Lord, Who listens to prayer”) (Sota 41a; MT, op. cit. 3:4).
This leads to another question: How could all the people assembled hear the king without a microphone? Perhaps in the women’s courtyard, which was closed off, 10,000 people could hear the king if his voice was strong. But if there were more than that, they would not have been able to hear him for such a long reading. Evidently, it was not necessary for everyone to hear him. This idea is supported by the requirement for the hard of hearing to attend (Leḥem Mishneh on MT, Ḥagiga 3:6). Even though they would not have been able to hear, they were expected to be there and imagine that God was issuing these commands at that moment. If this is correct, we may conclude that the halakha follows the opinion of the Sages (and Rambam) that the event took place in the women’s courtyard. Ten thousand people were there, and the rest of the nation stood on the Temple Mount. Even though an individual might not hear, he still completely fulfilled the mitzva. Alternatively, according to Tosafot (Ḥagiga 3a s.v. “af”), the mitzva does require each and every person to hear, which leaves open the question of how the masses could fulfill the mitzva. In any case, people in the future Temple will certainly fulfill the obligation, because the king will be able to use a microphone. See Peninei Halakha: Berakhot 12:9 n. 8.