One of the "Classic Eight Peaks" of the North Cascades, in the remote Chilliwack group so close to the border that the standard approach starts in Canada.
Drive into Canada via Highway 1 to Chilliwack/Sardis, then the Chilliwack River Road and the unsigned Depot Creek Road (watch for a locked gate around the 0.9-mile mark, and a fork requiring a left turn onto the older road bed). Park near the road's end and walk a way trail about 200 yards into old growth to the US/Canada border obelisk and trail register at Monument 65 — this is an informal, unstaffed border crossing on foot, not a designated port of entry, so carry a passport or NEXUS card and confirm current border-crossing requirements before the trip. From the border, follow the old trail up the Depot Creek valley; the route gets wet, noisy, and misty near a waterfall partway up. Continue to Lake Ouzel (about 5,700 feet), a good camp for both Redoubt and Spickard on flat, sandy, treeless benches, or camp lower in Depot Creek Meadow if splitting the approach over two days. From camp, gain the Redoubt Glacier (a shortcut via a large buttress exists if camped partway up the valley around 4,800 feet) and follow a line described as Redoubt Glacier-South Couloir-Southwest Shoulder-Southwest Chimneys-Cannonhole-Upper East Face to the summit — a long, multi-stage line combining glacier travel, a couloir, and rock scrambling.
Descend the climbing route back to Lake Ouzel camp.