The first four cuts are most easily done freehand; the fifth can be done more accurately against a steel rule.
1. Cut the vertical edges
2. Cut the downward-sloping diagonals
3. Cut the upward-sloping diagonals
4. Cut the horizontal edges and the rounded corners (but not the outline)
5. Cut the outline (with a steel rule)
6. Remove the cut-out pieces
It may be necessary to cut a little more at the corners of the small pieces during this step.
Be careful not to rip any of the thin areas.