There's so many spots to ski, but the parking on a weekend! North Shore, there is Tahoe Meadows. A fairly big parking area in summer at least with a facility allows access to Tamarack Peak and even Mt. Rose. You can easily ski the road on the hill that heads northward, it goes to the top of Relay Peak though to the old Mt. Rose TH it's pretty flat. There's Spooner Lake NV SP, but probably with a fee. My Northern Sierra Peaks Guide has exact though maybe old directions for the dirt road along the Carson Range Crest, as to Genoa Peak and further along.
Aside from the initial steep part, the road to Horse Meadows (also in the NSPG) is nicely gradual with some slight runs. Carson Pass runs you $5 of course, but if you can find a pullout down the hill to park, there's touring along Hwy. 88.
Big Meadow TH along CA 89 has a steep start, but the upper part is fairly flat. Lots of lakes and meadows up there.
Don't know if they charge at Taylor Creek, but we used to ski into Fallen Leaf Lake Road. That's about 5 miles to the end of the lake. All flat.
Don' think there's anything better but Castle Peak Exit, just pay the $5. A sizable meadow past the first .5 mile is great for snow play. More, but I just did 27 miles.