Island Peak is one of the handful of glaciated "trekking peaks" in the Khumbu. At 6189m / 20,305 ft, Imja Tse is a serious glaciated, high-altitude climb. The standard route has climbers heading from Chukkung to Base Camp and then usually summiting the following day. This FKT runs all the way from Chukkung to the summit (and back) in one fell swoop, though one could argue for a BC-Summit record as well if this route becomes more competitive.
The route itself is not tremendously complicated for an experienced climber. The terrain from Chukkung to BC is obvious and easily runnable (though it can be snowed over). From BC, the trail continues about 1km more fairly flat and then cuts steeply up to the left up some grassy/rocky switchbacks. This then goes up through a gully with significant rock fall danger if the route is not snowy, and then across to the right and then straight up a scrambly ridge for another couple hundred meters.
In November, 2023, the glacier started at around 5850m. From there, it is a short steep climb onto a big open and flat-ish snow plain until reaching the Headwall. Generally, I believe the headwall is snow and ice, though when I climbed in Nov 2023, there were about 40m vertical of rock in middle, with significant rock-fall danger. Otherwise, the headwall is not complicated with fixed ropes and slopes up to 60-70 degrees.
The final maybe 20m is on a very narrow ridge up to a tiny summit where you have spectacular views of Nuptse, Ama Dablam, and more.
Note, you do need a permit to climb Island Peak, but you are still allowed to climb without a guide as of Nov 2023.