This route is more of an interpretation of the terrain than a cairned, trailed route. It simply follows the line of least resistance up the west face, in a gully that ends about .2 miles due north of the summit area.
Park at the Long Scraggy TH off of Hwy 126 (daily fee area), hike or bike north along the highway about .25 miles, then head east on (closed) FR 530.
Follow the road as it winds down and avoids all of the private property. When you get to where you can begin to see the west face, you will be walking up a small rise - follow the terrain east and climb the series of ascending ledges, ramps, rocks, and terraces up the west face of LSP, choosing a line as easy or as difficult as you like. This will eventually put you on the north ridge route of LSP, about .25 miles from the summit. You will likely find cairns and flagging. Head south to the summit and enjoy the views.
Overall, there is no "trail", but the route goes well at 2+ or easy 3rd (but harder if you want).
From the west (as described), this is about an 8 mile RT hike/scramble.
Sturdy hiking shoes, daypack essentials, trekking poles. A map is useful.