Looking on the internet deeply has found these results:

on floor is the most popular phrase on the web.

on a floor 118,400,000 results on the web	on floor 121,300,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
I'm not laying on a floor. I just don't understand the appeal of trying to balance on a floor made of ice with two knives strapped to my shoes, waiting to fall down, which you know will happen. You decide on a floor yet? I worked on a floor called analysis. It goes on a floor, and... You left her to die alone, bleeding on a floor. The crime scene at Mercury Labs was on a floor with highly secured vaults, and the witness said he was looking for something.	We've got 100 people stranded on Floor Zero. I am proceeding along corridor 5673 towards section 301 on floor 34 north side. It's in their manual, right after "Love your grill, leave socks on floor." It was your code that accessed the medication case on floor five. Everyone on floor four is fired. Ladies and gentlemen, Payson Keeler on floor. Sit on floor and put together chair we will. Clearing out a bogey on floor five.

on a floor

118,400,000 results on the web

on floor

121,300,000 results on the web

More popular!

I'm not laying on a floor.
I just don't understand the appeal of trying to balance on a floor made of ice with two knives strapped to my shoes, waiting to fall down, which you know will happen.
You decide on a floor yet?
I worked on a floor called analysis.
It goes on a floor, and...
You left her to die alone, bleeding on a floor.
The crime scene at Mercury Labs was on a floor with highly secured vaults, and the witness said he was looking for something.

We've got 100 people stranded on Floor Zero.
I am proceeding along corridor 5673 towards section 301 on floor 34 north side.
It's in their manual, right after "Love your grill, leave socks on floor."
It was your code that accessed the medication case on floor five.
Everyone on floor four is fired.
Ladies and gentlemen, Payson Keeler on floor.
Sit on floor and put together chair we will.
Clearing out a bogey on floor five.