The 36-year-old, who shot to fame at the age of 11, has spent the past year renovating Rhydoldog House, the Mid Wales mansion which was once owned by the Laura Ashley family.
The seven-bedroom house near Rhayader, had been on the market for £1.5 million until it was bought by the opera-turned-popstar who has turned it into a nature-orientated business venture called The Dreaming.
The 36-year-old posted on Instagram saying she was "utterly delighted" The Dreaming was ready to take bookings.
"There is such joy in my heart that I can finally share this beautiful place with you all," she said. "I, along with many talented collaborators have worked tirelessly to bring this vision to life. I just cannot wait for people to experience it."
The Welsh singer-songwriter and self-professed "ecowarrior" says she plans to make the project "as accessible as possible" amid cost-of-living crisis, and revealed her hopes to make the retreat open to people from all backgrounds as she plans to develop "pay what you can" and "pay it forward" schemes.
She said The Dreaming Retreat's rooms are "all at different price points so people can access it".
She added: "One thing that was really important to me was to make it as accessible as I could. There will be a pay what you can space on all the retreats that we do."
She went on: "I really want to set up a pay it forward scheme, I really want to work with different charitable partners, so over this next six months to a year I'm really going to see what our options are to make this as accessible as possible and as useful as possible."
The renovation process is also being followed on TV show Charlotte Church's Dream Build, which airs on Really.
Church bought the property two years ago and has been engaged in the renovation project ever since, with the first series of the show airing last year and the second series having started on Wednesday evening.
The singer, who has previously performed for the Queen and former US president Bill Clinton, revealed that she will be a "practitioner" at the retreat, and plans to do "chanting and singing to the land" as part of the experience.
The renovated country mansion features a variety of themed rooms; these include The Moon, which contains a round bath overlooking the Moon Garden; The Mushroom, a room filled with botanical plants; The Wanderer, containing natural materials and artefacts from Africa, Peru and Mexico.
Church explained her motivation behind the project, saying: "I am such an eco-warrior, I'm sure a nature person, that's sort of what I'm really motivated to do anyway."
She added that the impact of the pandemic and other growing pressures on everyday people spurred her on to create a place where people are able to escape their busy lives and unwind.
"In part, it's about connection to nature," she said.
"In our busy lives we don't have time, people are so distracted by everything, our nervous systems are getting burnt out, our mental health isn't coping very well."
Church also said the retreat will be "gentle and self-guided," meaning guests "can access it at any level".
Three-day weekend and weekday retreats are offered with prices including all meals and wellbeing activities.
The first available dates are in January 2023 at thedreaming.co.uk.