One common place to read One Piece manga is through online manga apps or websites that have licensed the content. For example, Manga Plus is a popular choice. Just make sure you're accessing it from a legitimate source.
One popular option is to visit the official One Piece website. They might have authorized sections for reading the manga. Another possibility is to check out your local library. Sometimes they have manga collections that include One Piece.
You might find the One Piece manga on websites like Manganelo or MangaPark. But do keep in mind that these might not always be legal or have the best quality. It's better to go for official sources for the best reading experience.