I generally successfully avoid going to see blockbuster hit tourist sites between the hours of 11 and 3 pm.
What are the best times to visit to avoid crowds at Monet's house in Giverny if at all?
It's been a while since we were there. We stayed overnight in Giverny at a BnB. We got to Monet's Garden just prior to opening. At that time, tour groups used a side entrance that goes into the back of the garden and close to the water lilies. We used that entrance, and went to the water lilies first, then the house and then the rest of the garden. Tour groups got there between 9:30 and 10. Another guest had mentioned that they went late afternoon and that worked well, too.
If you have reserved tickets you use the tour group entrance. We went on October 31 last fall -- the last day for the season and did go to the water first. Early is good.