Shakespeare seems to draw attention to the poverty of material resources in his theatre. He won't let us forget this, making jokes at the expense of his "wooden O" -- which glances not only at the theatre's round shape and its small size but also at its nothingness, its status as a cipher.
Yet this is a bareness, a nothingness that has great potential. The Chorus to Henry V makes this clear in a metaphor from accounting:
O pardon! since a crooked figure
Attest in little place a million;
And let us, ciphers to this great accompt,
On your imaginary forces work.
Just as a series of 0's added to 1 can make a million -- 1,000,000 --- so too the imperfections of Shakespeare's theatre, pieced out with the imagination, can create grand scenes, kingdoms, princes.
Of course, this is a self-deprecating boast. It is not just the audience that makes something from nothing: their thoughts are shaped in the crucible of Shakespeare's dramatic art. So "O pardon!" is really "See what I can do!"
What is the effect of these metatheatrical moments in Shakespeare's plays? These are the moments which playfully jostle us from any state of suspension of disbelief, reminding the audience of itself and of the world underlying the one conjured by the play. "This green plot shall be our stage" (MND); "the groundlings ... capable of nothing but inexplicable dumbshows and noise" (Hamlet); "If I were a woman I would kiss as many of you as had beards that please me" ('Rosalind' in AYLII). These reminders that the play is a play seem not to detach us but rather to draw us further in.