Diana is buried on an island in the Althorp estate
In a candid interview with a local newspaper, Lord Spencer also revealed plans for an 18ft high urn on the island burial site at Althorp in Northamptonshire.
He said he had no regrets about the decision to bury Diana on the Oval island in the ornamental lake at Althorp following her death last August.
"I had been uncomfortable with the idea of the crypt and one morning I just woke and thought 'We'll bury her on the estate'. I talked it over with a couple of other people and we went from there."
The island has a simple temple which has been enhanced as a permanent memorial to Diana.
It contains two marble slabs with inscriptions and a profile of Diana. One will bear a quote from Diana herself, the other bears a quote from Lord Spencer's forthright funeral speech.
"The joy of that place is its natural beauty with its trees and plants. We are doing a lot of landscaping work in the park and around the temple and our personal memorial to Diana is transforming that site.
"It is also appropriate because water was her element - she was always very at home in it."
But Lord Spencer intends to keep the island private and there is no marking of the Princess's actual burial place.
The interview was given to the Northants Evening Telegraph and its sister paper the Chronicle and Echo.