I capture snowflakes at open balcony of my house, mostly on glass surface, lighted by LED flashlight from opposite side of glass, and sometimes in natural light, using dark woolen fabrics as background.
On a floor of a balcony I put the turned stool (legs up), on them - a glass plate. Previously, i shoot using Canon A650's standard macro mode. For this, from a small plastic bottle I cut central cylindrical part in the form of a tube (height 5.5 cm). This height I picked up so that the lens of the camera, pushed in a tube, will be at distance 1 centimeter from the bottom (this is minimum focusing distance of Canon A650 in macro mode). I just put this cylinder with the camera's lens within it over the chosen snowflake, the lens looks vertically down.
Recently, i built simple macro addon for the camera. I used lens Helios 44M-5 from old USSR SLR camera Zenit (here is short description in wikipedia). At first, i attached these lens at narrow wooden board (around 30 cm long), reversed: a back lens to snowflake, front lens to camera, and drilled in a board an opening for a screw suitable to tripod nest of the camera. Then camera is put on a board so that the lens in the maximum optical zoom mode (6x) touched Helios lens and looked straight into them.