Preheat the oven to 400 degrees F. Toss the sweet potatoes with 1 1/2 tablespoons of the oil and ¼ teaspoon each salt and pepper on a rimmed, greased (or parchment lined) baking sheet.
Roast the potatoes until lightly browned and tender, about 20 minutes, checking after 15 minutes and flipping if the bottom sides are sufficiently browned. Remove from oven and allow to cool slightly.
Meanwhile, in a small bowl whisk together the remaining 3 tablespoons of oil with the lemon juice, mustard, honey, and 1/4 teaspoon each salt and pepper. (Tip: To easily emulsify—i.e., combine and thicken– the dressing, simply add the ingredients to a jar with a tight-fitting lid, screw on the lid, and give it a good shake.) The vinaigrette may be made up to a day or two in advance and refrigerated.
Place the kale in a large bowl and sprinkle with 1/2 teaspoon salt. With clean hands, rub the leaves together or “massage” to tenderize the leaves. After a minute or two, you will notice the leaves turn a darker shade of green. Then add the apple and sweet potatoes, pour the prepared vinaigrette over top, and toss to combine. At this point, the salad may be refrigerated until ready to eat. Prior to serving, toss the salad again and sprinkle with the chopped almonds.
When tightly covered with plastic wrap or stored in an airtight container in the refrigerator, the salad will keep for at least 5 days.