The lens itself doesn't have a tripod mount. This is problematic, because you're essentially running a 3.5 degree horizontal angle of view from behind. What's that mean? If the center of rotation is at the camera (tripod socket or handheld), any motion is maximized at the front of the lens. At minimum, you're working the OIS harder, but even with OIS turned on I find that you can still get unwanted camera motion in shots. If you move the rotation of the lens/camera to the center of gravity or optical center of the system, the same level of vibration tends to be reduced by about half. With care and discipline, it can be reduced to zero.
With the large DSLR systems and very long lenses, most of us use tripod mounts on the lenses for our support, and some of us go further and use a product like the Really Right Stuff Long Lens Support to take out even the tripod mount vibration. Basically, we're trying to make everything (tripod, head, mount, lens, camera) into as close to one solid mass as possible, with no loose joints that induce any vibration or pivot capability. And we use gimbal heads that rotate at the center of the mass. I can get the RRS solution to quasi-work with an m4/3 body and the 100-300mm by using a double clamp under an Arca style plate on the body, but this is way overkill: you end up with a lot more weight and parts, and a plate that sticks out back behind the body that's cumbersome.
The real issue is that the 100-300mm doesn't have anyplace to put a front support. The zoom ring and focus rings are back-to-back, leaving only the protruding inner barrel to rest a front support on. Unfortunately, that inner barrel moves in and out as you zoom, and you don't want to torque it by putting pressure against it.
There's only one solution I've seen that comes close to being ideal, and that's a hand-crafted ring/shoe that attaches behind the zoom lens, made by someone in Germany. But I've not tested it. If you're okay with leaving the lens at one zoom position, the Manfrotto 293 Telephoto Lens Support might be worth trying, but be very careful to not adjust the front support and strap so that the lens barrel is pulled off of center.