"The stone cutting machine is over there, and there's water from the well here, you can use it as you please."
As for what the raw stone material that Huo Sining wanted to cut looked like, the owner didn't bother to look closely.
First, he needed to attend to the business at the front of the shop and didn't have the leisure to care;
Second, he saw that both Huo Sining and Bai Yishan were novices and thought the probability of their gambling on the rise was too small; watching the two women perform stone gambling wasn't very interesting, knowing they would likely cut it wrong. By hanging around, he would only be a nuisance; better to keep an eye on the shopfront.
Although the owner didn't seem like a mean-spirited person, it was necessary to be cautious. Huo Sining and Bai Yishan were both fragile young women—if the stone's value increased once they began cutting and the owner saw it, if he became greedy, they certainly wouldn't be able to overpower him.