Place the sliced cucumbers in a bowl or colander and toss with kosher salt. Let them drain for about 1 hour, then gently blot with a clean towel to remove excess surface moisture.
While the cucumbers drain, make the dressing. In a small mixing bowl, combine the low-sodium soy sauce, rice vinegar, creamy peanut butter, honey, minced garlic, crushed red pepper flakes, and black pepper.
Whisk for 30 to 60 seconds, or until the dressing is smooth, creamy, and fully blended. Let it sit for a few minutes so the garlic and red pepper flakes can infuse the dressing.
Transfer the drained cucumbers to a clean bowl. Add the toasted chopped peanuts, chopped parsley, and spicy peanut dressing.
Toss gently but thoroughly, lifting from the bottom of the bowl until the cucumbers are evenly coated and the peanuts and parsley are distributed throughout.
Serve immediately for the crispest texture, with a little extra parsley on top if desired.