First of all, decide whether you want hot pepper relish (remove the seeds from the Hungarian peppers) or hot, hot, hot pepper relish (leave the seeds!).
Chop the peppers either by hand or using a food processor. Place the chopped peppers in a pot with the mustard, vinegar, sugar and salt and boil on medium-high heat for 15 minutes, stirring occasionally. Add the flour, ¼ cup at a time, stirring constantly.
Place the relish in the jars, add the lids and rings and process in a hot water bath for 5 to 8 minutes.
Special equipment: 8 hot, sterilized pint-size jars with lids and bands, Water bath canner or lidded pot large enough to hold 8 pint-size jars covered by at least an inch of water