Speaking to the club website, the 54-year-old claims he was not thinking about a return to management following his stint in charge of Shanghai Shenhua, but that he could not resist a chance to return to a place he described as "home".
"I was in Madrid," said Sanchez Flores.
"I'd just arrived from an experience really far [away] and I was thinking to watch football and rest and take time for my kids.
"It was impossible to say no. I was in my house and received a call and I was really interested to know what Watford need and if I was able to do something for them.
“You always think about how to recreate your best dream. To come back to Watford wasn't exactly a plan but it was a possibility because of my memories and the happiness. I had good people around and an amazing feeling with fans. It was really easy to say 'yes'.
"I loved the way the fans love football in England, the way they support and the way they respect rules in England and everything. The moment I left I was waiting for the moment to come back to England. I feel Watford is my home."