Fold a water bomb base. (Click on the link for instructions)
Folding the flaps
Lift the front western flap of the water bomb base, and fold it so its point meets the northern point of the water bomb base, crease. (The overall model should currently look like the triangular water bomb base with the front flap of the western right triangle section folded so its points touches the northern point of the model)
Fold the point of the front western flap back so that it meets the base of the flap, crease and unfold. (Now there should be a valley fold line half way down the western front flap)
Again, lift the point of the front western flap, and fold it down to meet the crease created in the last step, crease and unfold. (Now there should be two valley folds in the western front flap, one 1/2 down the flap and one 1/4 of the way down the flap.)
Repeat the last step on the eastern front flap. (Now both of the front flaps should be folded up to meet the northern point of the water bomb base, and both should now have two valley folds 1/2 and 1/4 of the way down both of them.))
Flip the model over, and repeat the previous two steps on the two unfolded flaps on this side. (After this is complete, all four flaps of the water bomb base should be folded up to meet the northern most point of the model, and the overall shape now should resemble a rhombus, in addition, all flaps should also have the two valley folds 1/2 and 1/4 down there length.)
tuck in the flaps
Fold the southwestern corner of the front west flap so that it meets the central north/south crease, crease. (The front western flap should now resemble a sideways trapezoid with a triangular pocket like flap folded on top of it, along with the two valley folds created previously.()
Lift the triangular pocket flap created in the last step, and separate the two layers of the flap to create a opening. (the triangular flap off of the west front flap should now be slightly open enough to allow a insertion of another flap.(
Lift the two northern sub flaps, of the west front flap, created by the two valley folds, and tuck them into the pocket flap, that was opened in 3.1.1, then squash down the flaps. (Now the front western flap should resemble a folded parallelogram with a second flap tucked into it’s top)
Repeat the entirety of 3.1 on the eastern front flap. (On the front of the model, both of the front flaps should be folded into parallelograms with there top halves tucked into there tops.)
Flip the model over, and repeat the last two steps on this side of the model. (The main model of the balloon should now be complete, it should resemble a oblong hexagon with the points alined to north and south, the east and west halves are composed from two of the now folded trapezoidal flaps with a small hole at the southern point.
Inflate Your Balloon. Gently blow into the hole in the southern point of the model, if all goes well, the model should inflate into a roughly spherical shape!