Mix the yeast, 3 cups water and honey or sugar in a big bowl, and let the mixture bubble for about 5 minutes.
Add the eggs, oil and salt, and beat.
Add the flour, and mix thoroughly adding more water as needed up to 4 cups.
Transfer the mixture to a lightly-floured flat working surface, and knead for about 15 minutes, turning the dough a quarter of a turn every 2-3 minutes and punching it down often to eliminate any air pockets (or transfer the mixture to the bowl of a dough maker. Set for 10 minutes of kneading).
Transfer the kneaded dough into a big mixing bowl (remember, it will expand).
Sprinkle flour all around the dough.
Let rise, covered with a cloth, in a warm draft-free area for 2 hours.
Shape the Challah: divide the dough into 4 pieces.
Divide each piece into thirds and roll each third into a long thin rope.
Pinch the 3 ropes together at one end to hold them in place.
Braid, and place the braid on a foil-covered cookie sheet.
Repeat with the rest of the dough.
Place the loaves well apart in the pan (you might need more than a pan: Bake one at a time).
Brush each loaf with the egg-and-water mixture, and top with seeds if desired.
Bake in a preheated 350*F oven for 45 minutes to 1 hour.
