Stitch the knots around the outline first. It's not always possible to line the knots up in a grid pattern, especially if the shape itself is rounded or irregular.

When stitch the knots in the interior of the shape, place the knots as close to each other as possible. You'll need to use your judgement to determine if a particular "hole" in the shape is big enough to stick a knot in it.

If a "hole" is slightly too big for a knot, but not big enough for two knots, consider filling it with a Multi-wrap French Knot.