I thought I was a pantser when I was younger, but seeing as the only two big projects I've ever finished were thoroughly plotted beforehand, that was inaccurate 
I'll plot out the story in a decent amount of detail before I start writing anything, as well as character descriptions and backstories. I'd say that 85% of the scenes in the final first draft were explicitly included in my outline. A few get cut, a few get added, and on my more recent project I actually added a whole little arc that wasn't planned. That outline had 60 bullet points, which turned out to be a good level of detail for me. Enough that I never got stuck, but little enough that I had room to discover the characters' emotions and such along the way, even though the events were figured out.
The key for me is to marathon the writing part. I can spend a couple days or a couple weeks on the outline, leave it for a few days and come back, whatever. But once I start writing, it's a marathon. I don't skip days. Together, plotting and marathonning work for me for two reasons:
1. Writer's block is mainly mitigated by having the outline. Even if I'm totally uninspired by a scene, I can at least grind out something really rough and come back to it later, then get on to more exciting things. If I don't have that outline already, I just... stop. And never come back. I get stuck on that moment and don't know what the more exciting things are that I'm working towards, so I just drop it entirely.
2. By writing a ton over a short span of time, I don't lose track of things. I remember what's happening, things that need to be worked in, etc. When I take breaks, even just a day or two, I start to lose the thread of the story in my head as well as the motivation to finish.
Before figuring this out, my longest project was an unfinished 26,600 word trying-to-be-a-novel that I worked on over three years. With the system above, I first wrote a 40,000 word novella in about three weeks (which I'm now posting on Tapas - Life in Polaroids), and more recently finished a 94,000 word novel in a month and a half (which, fun fact, is a very revamped version of the 26.6k piece mentioned earlier).
Both stages are very linear for me, especially with my most recent work. I started the outline with no idea how it would end, and I didn't know until I'd worked through almost the entire thing. I write from beginning to end, following that outline and adding as needed.