I was trying to join (by heating) a couple of small solder spheres (BGA) on the hot plate. But in the end, I always obtain a flat surface where the sphere was touching the substrate.

Is there any method for the fast and easy creation of solder spheres?

For example, on the market, the biggest solder spheres (BGA) available are 760 um. How can I get/make a bigger one? Say 2 mm?