Read the supplement to this article which discusses the various designs of shuls in terms of the placement of the Shulchan and duchan as well as the nomenclature used throughout time.
He states that Rambam suggests that everything should be in the middle of the shul, but there are few people / places doing that mainly b/c of space and design constraints. Thus, a suitable option was to have a dais next to the Aron. Excerpt:
The dais occupied a great deal of room, preventing those whose place
was behind it from seeing and hearing. In order to eliminate both
problems, most modern synagogues have no almemor in the middle; thus,
more room for seating is available for worshipers, and everyone has an
unobstructed view of the precentor's desk and the ark. The new
arrangement came up against considerable opposition, and had to be
justified by numerous rabbinical opinions, but in view of its
practicality it has come in nearly everywhere. In America, Germany,
and Austria-Hungary, synagogues are only rarely built with the almemor
in the middle, but rather the dais is placed directly before the steps
leading up to the ark. On it stand the precentor's desk (also called
cenr) and the reader's table, with the former facing the ark and the
latter, the congregation. In a few rare exceptional cases these are
the same. Another furnishing of the dais, since ancient times, is a
chair (`qk) or bench on which the person sits who holds the Torah
while it is being rolled and awaiting its return to the ark. In
ancient times the sermon was delivered from the dais, and in the Greek
synagogues the speaker used a special platform; in recent times the
platform is situated directly before the ark or, in individual cases,
on a pillar by one of the side walls.
In most shuls I have attended, including my current one, there is a lectern on the bima, and when the rav gives his drasha from the lectern, his back is towards the Aaron facing the congregation.
My current shul is somewhat unusual in style as the table is in the back of the shul (Sefardi style) and there is only one table that is used bith for davening and Kri'at Hatorah. There is no shtender *lectern) in front of the shul below the bimah.
Another shul in my neighborhood has no bimah - everything is on the same level. One lectern is to the right of the Aron where davening is done. The rav sits to the left of the aron. There is another larger table in the middle of the room for Torah reading and this is where the rav delivers his sermons from. His back is to the aron when he speaks.
