Where is the fuse box in a Lexus ES300?

Answer

It's located on either the right or left side of the engine.

At least in the 2002 ES 300, there are two fuse boxes. One is under the hood, a long black box with a removable lid on the driver's side, above the wheel well. The second is also on the driver's side, inside the car, close to the door; left side of steering wheel on the under side of the dashboard behind a hinged pocket-door that comes out if you open the pocket-door and pull gently it up and out, which allows the pocket-door to snap out of the hinge detents. At which point you'll see the fuses hiding behind.

P.S. There is a white plastic fuse puller tool that you can use to facilitate grabbing hold of a fuse to remove and inspect it which is in the fuse box under the hood, previously mentioned.