Measure 3 cups sugar into a large bowl. Remove ¼ cup sugar and in a separate bowl, mix it with the powered Sure-Jell. Set aside both mixtures; the sugar and Sure-Jell/sugar.
Roughly chop all of the peppers. Carefully remove seeds and membranes. Add them all to the food processor and pulse until they are well chopped, not pulp, but chopped. You may need to do this in a couple of batches.
Place the chopped peppers, red pepper flakes and salt in a heavy bottom pan. Add cider vinegar and water. Add the Sure-Jell/sugar mixture and stir thoroughly. Place mixture over high heat and bring to a boil stirring constantly. When it comes to a full rolling boil (one that you can't stir down add the remaining sugar and return to a boil, again stirring constantly.
Bring to a hard boil and boil hard for exactly one minute and remove from heat. Using a ladle and while it is hot, pour jelly into hot sterile jars.
Clean the tops of the jars carefully (so you get a good seal). Place lids on jars and screw bands on jars.
Place jars in boiling water bath for 10 minutes - this will help seal the jars. Make sure the entire jar is submerged.
Remove from heat and place them on a heatproof surface (I usually use a heavy cutting board. You'll hear the jars make a popping noise as they seal. You can check to see if the jars have sealed by pressing down in the center of each jar. If it is sealed, it will not move. If it didn't seal the "button" on the top will pop up & down.
If desired, you may want to flip the jars over ever 20 minutes or so for the first hour. This ensures the pieces of pepper will distribute evenly thru-out the jam. If you don't, they will all float to the top. Now there's nothing wrong with that, it's just an extra step that makes the jam look a little prettier when it's done.