With patterns it’s important to make things flow nicely, so I’m having a seemingly neverending river running diagonally across the design. Working diagonally also helps when lining things up. Draw the river roughly using the Pencil tool (N) or the Pen tool (P) from corner to corner – or open River.ai from the cover CD.
Because the pattern needs to tile, any objects that go up to the edge of the square need to match up on the other sides. To do this, copy and paste the original and place the copy in the bottom right hand corner. You’ll see that the two ends of the river don’t line up so we need to change this to get the pattern to flow.
Join the two ends of the river by selecting them with the Direct Selection tool and press Cmd/Ctrl + Alt/Opt + Shift + J. Select the Smooth option. Play around with the anchor points to get a smooth line. Outline the whole stroke: Object > Path > Outline Stroke.
Now we need get rid of any pieces that extend beyond our square. Select all (Cmd/Ctrl + A). Click the Divide button in the Pathfinder palette. This will make each shape a separate object.