Apply the Unna boot to clean, dry skin with the patient comfortably positioned and the limb elevated to reduce swelling. Begin with a thin layer of zinc oxide or prescribed paste over any open areas, then wrap a nonadherent dressing or gauze over wounds as directed. Place a padding layer (soft roll or cotton) around bony prominences, especially the heel and ankle, to prevent pressure points. Hold the foot at a 90-degree angle and start the Unna paste-impregnated gauze at the toes, overlapping each turn by one-half to two-thirds, and continue up the calf to just below the knee. Keep tension firm but not constrictive—support venous return without blanching or numbness. Smooth each layer to eliminate wrinkles, and finish with an outer cohesive or elastic bandage for additional compression and to secure edges. Reassess circulation, sensation, and comfort immediately after application and instruct the patient to keep the boot dry; change per clinician orders (commonly every 7 days) or sooner if soaked, loosened, or if signs of infection or ischemia appear.