Word problem with real world application

Hi all, I've got this word problem which represents a schedule for a dart league. Is there an easy way to go about completing it? Its giving me trouble...
There's 12 people who will be grouped in threes for 11 weeks so they can play each other twice.

Carl has 4 boxes and 12 gerbils.
Each day Carl puts 3 gerbils in each box.
He does this for 11 straight days but no gerbil is in the same box as any other gerbil more than twice.
Numbering the boxes 1 through 4 and the gerbils 1 through 12, show the boxes and gerbils for each day.

If anyone can help I'd appreciate it. Thank you!

What do gerbils have to do with a dart tournament?!

Nothing. I just made up a word problem to go along with it. I found it more interesting.