Directions

1. Wash the cucumbers, remove the seeds and grind them along with the peeled onions using a meat grinder or grinder attachment on your mixer.  Put the ground cukes and onions plus all the juice that accumulated in a plastic or glass container and sprinkle with the coarse salt, adding ice cubes or really cold water and mix to distribute.  You want to have enough liquid to come up to the top of the cuke and onion mixture.  The salt will draw out the moisture from the cukes so be sure to leave room for that.  Refrigerate overnight or for at least 8 hours.
2. Next, drain all the liquid from the container using a colander. Then strain the mixture through a section of nylon pantyhose (I buy pantyhose at the Dollar Store specifically for canning :)).  You want the mixture to be well drained but still moist.  Remove to a large roast pan and place on the stove.
3. To make the mustard combine the flour, sugar , turmeric and dry mustard in a separate saucepan.  Blend in the vinegar using a whisk.  Cook stirring constantly until thick.  Remove from heat.
4. Add enough of the mustard to the roast pan containing the cuke and onion mixture to make a nice thick relish.  Bring to a boil then reduce heat and simmer 20 minutes.  Using safe canning practices put in jars and process in a hot water bath for 10 minutes.