Warning: This produces small amounts of chlorine gas, this should be done outside or in a fumehood.
Potassium chlorate is a useful oxidizer and small amounts can be easily made using household chemicals. Start by boiling a large quantity of household laundry bleach, at least half a liter, until crystals start to precipitate. Immediately take it off heating and let it cool. As it cools make a saturated solution of potassium chloride. Potassium chloride is sold as a "sodium-free" salt substitute. Now once the bleach is cooled, measure out an equal volume of potassium chloride solution and pour into the boiled bleach solution but do not mix in the crystals. Stir up the mixture and eventually potassium chlorate crystals will precpitate out.
What's happening is the sodium hypochlorite in the bleach is disproportionating to form sodium chloride and sodium chlorate. Adding the potassium chloride exchanges the ions and precipitates out potassium chlorate.
The boiling is required for this reaction to work; you can't simply let the bleach evaporate.