The Spaniard, who became the club’s fifth manager in a year when he joined two months ago, has overseen the arrival of 10 new players.
However, despite the club’s hectic transfer window, Watford are odds-on favourites with the bookmakers to be relegated back to the Championship.
Flores disagrees and said: “We are ready for the start of the Premier League.
“We have worked very hard in the last five weeks to get a high performance against Everton and give our best for the first match.
“I have every confidence with the players. I am seeing every day how they are working and how they want to show themselves in the Premier League so I am really confident with these players – it is an amazing group and I am very happy with their work.
“Last year is finished, last year was enough for promotion, but everybody knows that it is not enough to play in the Premier League so we need to get a new step, a new level.”
Flores also believes the club’s multilingual dressing room will play to their advantage this season.
The newly-promoted Hornets, who travel to Everton on Saturday for their first game back in the Premier League since 2007, boast 22 different nationalities.
The former Atletico Madrid manager replaced Slavisa Jokanovic in June and has spent more than £20m on ten recruits who have arrived from France, Greece, Holland, Austria, Lithuania, Switzerland and Spain, to form one of the game’s most diverse squads.
“I think this is an advantage for us because when you are training more English players, maybe it is difficult to change but now I can change any habits very easily,” Flores said.
“Sometimes it is strange because when talking in English I can talk in Spanish with Spanish, Ecuadorian and Mexican players so sometimes we mix but it is a funny moment.
“I’ve never had it before, so many different nationalities, it’s the first time but a good experience.”
Flores, who confirmed English will be the main language in the Watford dressing room, added: “We live in England and all of the players understand English.
“The most important thing is the atmosphere we can create in the dressing room in terms of they have a good relationship with each other.
“They are fighting for positions but always as friends in a good way so for me it is perfect.”