3 fingers up-top. Index on Mouse1, middle finger on scroll wheel, ring finger on Mouse2 and pinky resting on that blasted right-side bump of the mouse. Cuz i have Kone Pro Air Wireless on my table, it was the 1st lightweight wireless mouse i bought like 2-3 years ago, and this shape seems to be specially made for 1-3-1. Absolutely unusable for fingertip XD
Edit: Also, while the mouse does have a lot of good features (apart from the shape, obviously, which is subjective, so w/e), the main buttons with their optical switches are objectively trash compared to most other lightweight wireless mice on offer.