Marinate the shallots. Mix together the shallots with the sumac, vinegar, and salt in a bowl. Use your hands to combine and allow to marinate for at least 15 minutes, or up to 30 minutes.
Shaved the cucumber into ribbons using a Y-shaped vegetable peeler. Slice the Little Gem lettuce heads into quarters.
In a bowl, combine the shaved cucumbers, parsley, mint, and scallions. Lightly sprinkle with salt. Drizzle the olive oil and lemon juice and gently toss to combine.
Transfer the salad to a serving platter or bowl. Top with the quartered lettuce heads. Spread the marinated shallot slices on top and scatter around the chopped almonds. Toss gently and serve.