'Kosher' does not mean 'clean'. It is sometimes translated that way, for want of a better word, but that's a poor translation.
For instance, a kosher mikvah can be made of very filthy water, such as in emergencies or, if you're stuck in the middle ages and have little choice.
Kosher chicken requires slaughtering by someone who knows how to do it according to kosher laws.
Kosher cow meat is much more detailed than chicken, and probably impossible to do it right unless trained by someone who knows how to do it.
For slaughtering cow, and animal in that category, there are five invalidations for the cutting:
1. pausing, she-hee-ah. If you pause the knife while cutting, not kosher.
2. pressing down, drassah. If you just press the knife into the neck, not kosher.
3. cutting from inside, chalada. If you stick the knife inside the neck, then turn it so that it cuts from inside to out, not kosher.
4. swirving, hagramah. If you don't cut straight along a specific line, not kosher.
5. tearing, ikur. If the knife is not perfectly sharp, as defined by a certain test involving the fingernail, I think, then not kosher.
That's just for starters, the animal has to be free from certain lung defects, it can't be dying, the blood has to be drained a certain way, certain nerve veins have to be taken out properly, etc etc. If you've ever heard of 'kosher salt', they call it that, not because some salt is not kosher, almost all salt is category one, kosher without certification I think. Rather, 'Kosher salt' is salt with large crystals so that it can be used in the 'kashering' process of taking meat slaughtered properly and then extracting the blood and dumping it in the trash. So, 'Kosher salt' is another way of saying 'salt with large crystals', I think.
Chickens are far less detailed, but still require certain details of which I am ignorant, and I'm pretty sure the blood must be drained.