Do not under any circumstances attempt it with a dremel!
Handsaw is way easier, trust me, even if you think you’d mess it up it’ll still be better than messing it up with power, with 100000 tiny cuts. Just take your time, and cut fairly shallow so that the length of the saw tends to keep you straight, and try not to cut your leg off.
Tracksaw would make it super easy and yep see if you can find one that has one, everyone on STW has one parked beside their woodburner. Just the ideal tool for the job.