Which gate is discussed?
Rashi: It is the north gate.
How big was Ulam ha'Sha'ar?
Vilna Gaon: This is the Ulam that every gate had 1 , which extended eight Amos.
Malbim: Its length was 10 Amos from east to west; its width was six Amos from north to south.
There were also Ulamos between adjacent cells. Ulam ha'Sha'ar was outside of all the cells, so it is attributed to the gate. (PF)
Where were the tables?
Rashi: Two were to the east [of Ulam ha'Sha'ar], and two to the west. Even though they extended into Chatzer ha'Chitzonah, their Kedushah was like inside [Chatzer ha'Penimi]. Malbim ? therefore, they were Kosher even for Shechitas Kodshei Kodoshim, which require the north of the Azarah.
Why does it say "Lishchot Aleihem" (with an Aleph, to them)?
Radak: This is like Lishchot Aleihem (with an Ayin, on them). Also "El he'Harim Lo Achal" (18:6 is like Al he'Harim) and many similar verses.
Why does it specify Olah, Chatas and Asham?
Radak: The Torah commands to slaughter Chatas and Asham in the north, just like Olah, lest sinners be publicized. (People do not know that he offers Chatas or Asham; perhaps it is an Olah!)