How can I make a DIY flea killer?

Hi.. Ruddy flies..i have cats an use broadline to kill them buying it from vets ..shop bought flie stuff. Dok martian DONT WORK such a waste of money..now if you have flies on carpets an sofas chairs you wil need a flie spray from the vets ..it kills all flies..strip all beds an wash on a boil wash cusion covers ect..cat or dogs bed also boil wash..hovering is next step..the vibrations make the eggs hatch ..hover every courner under the beds an the beds everywhere keep it going for a week CLEANIMG HOOVER AFTER EACH USE ..comb animal out daily to remove eggs an larvie ..with a flie comb...also a good trick to see how bad the prob is...a bowl off dishwater next to a candle..the flie will be attracted to the heat an drown in the water..another trick i learned...combing cats ...have hot water close comb the cat ..when you get a flie drob it into water..wet your comb with your fingers to clean but also they stick to the comb..making them easy to catch ..hope it helps

Here's what one Hometalker recommends

https://www.hometalk.com/diy/outdoor/pest-repeller/homemade-flea-repellent-for-home-13368995

It is not DIY but we had a terrible flea problem and tried everything. This is the stuff that finally worked! https://amzn.to/33vUkTS