The founder of an alleged New York sex cult held meetings in which female 'slaves' gathered naked on the floor around him while he sat in a chair and lectured them on philosophy, one of the women testified at his criminal trial on Friday.

The former 'slave,' Lauren Salzman, told jurors in federal court in Brooklyn that the group's leader, Keith Raniere, would preside over the meetings fully clothed.

When he was unable to attend the meetings in person, the women would take a naked photo and text it to him - making sure he could see where they had been branded with his initials, Salzman said.

'We were to look uniform and happy,' said Salzman, 42.

Lauren Salzman and her mother Nancy have pleaded guilty to taking part in the scheme to recruit members into the upstate New York group

Nxivm cult leader Keith Raniere, 58, is pictured. He faces charges including sex trafficking and child pornography for allegedly using his self-help group

Salzman first met Raniere through her mother in 1998, when she was 21, and soon began a sexual relationship with him that lasted for years.

'For me, it was a monogamous relationship,' she testified.

She said they stopped being intimate around 2008 or 2009 — when the alleged sex cult was in full swing.

Before their relationship started, Raniere examined how she looked in her underwear and told her she should weigh 100 pounds, Salzman said.

Raniere is also alleged to have snapped naked, up-close photos of her private parts and forced her into threesomes with other alleged slaves, including 'Smallville' star Allison Mack.

'I considered him an authority on almost everything,' she said. 'Initially, I participated because I was curious, but later i gave in to the romps because he wanted that.'

She described years of emotional abuse by Raniere, who had relationships with other women but forbade Salzman from dating anyone else.

Eventually she managed to break things off by around 2013.

'He told me that if I stayed he would invest in our relationship and we would have children,' Salzman told the court.

In one incident, she wrote a seven-page, single-spaced plan of atonement after he berated her for what she called 'rough-housing' with another man during a volleyball game.

Raniere, who was known as the 'grandmaster,' was furious.

'He said, "You straddled him!'' Salzman said.

In her 'plan,' she conceded, 'I'm perceived as easy or available.'

'This degrades me and sets a bad example for the organization and reflects poorly on Keith and his choice to be with me,' the 'plan' also said.

Salzman also laid out her own culpability, telling jurors how she, Raniere and others held a woman captive inside a room for two years under the threat of sending her back to her native Mexico.

She acknowledged recruiting slaves for Nxivm's secret sorority known as DOS, and extorting them by demanding compromising material, like nude photos, that could be used as blackmail if they refused orders.

If convicted of federal charges including sex trafficking and child pornography, Keith Raniere faces life in prison. He is pleading not guilty to all charges

Salzman said some believed he could affect the weather, echoing the testimony of another former member. If he released a new curriculum, for instance, that might create a big storm, Salzman said.

People also believed technology acted 'funny' around Keith because of his 'energy,' Salzman added.

Salzman, whose mother, Nancy, served as Nxivm's president, was a 'first-line slave' within DOS, which meant she answered directly to Raniere and had slaves of her own, she said.

Other first-line slaves included former Smallville actress Allison Mack, who like Salzman and her mother previously pleaded guilty to her part in Raniere's crimes.

Another first-line slave was a woman whom authorities have accused Raniere of sexually exploiting starting when she was only 15 years old, Lauren Salzman testified.

Raniere is also alleged to have snapped naked, up-close photos of her private parts and forced her into threesomes with other alleged slaves, including 'Smallville' star Allison Mack, pictured

Raniere, 58, faces charges including sex trafficking and child pornography for allegedly using his self-help group, Nxivm, to hide a secretive sorority known as DOS in which young women were forced to have sex with him, follow dangerously restrictive diets and obey his every command.

If convicted of the most serious charges, Raniere faces life in prison.

His lawyer has argued at trial that the women became members of Nxivm voluntarily and were never coerced into doing anything against their will.

Witnesses at the trial, which began last week, have detailed how Nxivm's teachers portrayed Raniere as 'some kind of god' who would unlock a more fulfilling life for his followers.