The phrase "a matter of sitting" is correct and usable in written English.
It can be used to indicate that something is simply about the act of sitting or involves sitting as a primary action or consideration.
Example: "For some people, meditation is just a matter of sitting quietly and focusing on their breath."
Alternatives: "just about sitting" or "simply involves sitting".
"Then it was just a matter of sitting there and seeing how far our system could go.
"It wasn't a matter of sitting around and saying, 'Oh, we must do Ionesco on Broadway' " Mr. Thompson said.
Then it's just a matter of sitting down and being rational and talking about how much it costs.
Yet for Lady MacMillan, owning the repertoire isn't a matter of sitting back and counting royalties, it is a commitment to watching over the companies who currently dance the ballets, supervising the mounting of new productions and opening up fresh opportunities for their staging.
It is a matter of sitting down and talking".
For Karen, it was a matter of sitting down with her husband and looking at their family finances.
The problem, as with so many things, is a matter of degree — sitting too much.
Many young hobbits were included, and present by parental permission; for hobbits were easy-going with their children in the matter of sitting up late, especially when there was a chance of getting them a free meal.
It is so much more convenient for them to represent media studies as just a matter of ignorant chavs sitting around watching telly.
On the other hand, these threads were usually very easy to gather up, a matter of the Queen sitting on her throne, her ministers assembling at Westminster, great landowners administering their estates, and a handful of financiers controlling the money supply.
I obtained this information in a matter of weeks by sitting at a computer in my office in San Diego and by picking up the telephone.
