piling, ceremony radical (no. 56)
弋 centers on a stake or post driven into the ground, used in ancient ceremonies or as a marker. The radical sense is the same stake shape used as a component in other characters.
弋 is a pictograph of a stake or post with a forked top, used for tying or marking. The modern form retains the basic stake shape.
The shape looks like a wooden stake driven into the ground, with a short top stroke as the fork and the dot as a marker. Picture it used in a ceremony to mark a sacred spot.
For ヨク, imagine a yoke placed on the stake: yoke -> ヨク, and the stake holds the ceremony together.