Grounded contains secrets that you can skip hundreds of times without ever finding them. The famous lucky clover is certainly the most notable example of this. This is why we are going to give you very precise indications.
Preparations
You will have to cross a dark and flooded cave to reach the clover. You therefore need a light source, such as an aquatic lamp, or the firefly headlamp helmet, in order to find your way. The cave is rather long, so without it you risk drowning. Turning up the game brightness (gamma) to maximum can also help, if you like to cheat a bit. Provide enough light to go there and back, you also have to swim back after finding the clover.
Position of the cave entrance
The clover is in a cave in the flooded area to the east. The easiest way is to start by locating the can of Chop, which is not very far (watch out for spiders). Then go east, looking for clovers at the edge of the water.
You have to look for a dead leaf that forms a kind of separation in the puddle. It separates the entrance to the underwater cave, which explains why it is almost impossible to find it while swimming normally in the puddle.
Here is the exact position of the entrance on the world map.
All that remains is to dive with a light source, and navigate the twisted guts of the underwater passage, in order to reach the cloverleaf, which will automatically unlock the Flower Executioner mutation. As a bonus, the cave contains Brittle Marble, Brittle Quartzite (Hammer 1 required), as well as their solid version (Hammer 3 required).