Prepare farro according to package instructions. Drain any excess cooking liquid and toss hot farro with arugula and pesto. Refrigerate in a large bowl for at least 20 minutes or until cooled.
About 15 minutes before you are ready to serve, add strawberries and feta and toss to combine. Drizzle lemon juice and olive oil over the top to finish and toss well.
Season with flaky sea salt if desired. Serve cold or room temperature.