In a very large bowl, add the yeast and the water. Mix until all is dissolved.. Then add the salt, molasses, shortening, seeds, and rye flour. Mix. Slowly add only 2 cups of flour. Mix and slowly add the rest of the flour. Mix. Put the dough onto a floured board and knead for 5-10 minutes. If the dough is to sticky add a little warm water. When the dough feels right, oil a large bowl and place the ball of dough in the bowl and coat the dough all over. Cover with plastic wrap. Place in a warm place for about 45 minutes to one hour. At this point dough will double in size. Place dough on to floured board and cut in half. Take each piece and knead then shape into a round loaf. Grease a large sheet pan and place each round loaf on the pan. Make sure that you leave enough room between the loaves Cover again and leave in a warm place, this should take about 45 minutes, to an hour. Preheat oven to 375 degrees, and bake for about 35 minutes. Remove and cool on a rack.