I found that I needed to make my own hooks by bending flat steel straps. An important addition to the plans is the addition of the backing plate inside. I used some scrap plywood and fender washers. My last bucket lasted about 7-8 years until it was stolen, so I've also added a way to lock it to the bike rack.
If you put the hooks at the right level vertically then the top of the lid is level with the bike rack allowing you to securely strap even more stuff on the back of the bike.