There are two main types: ski sleds and skate sleds. Due to the lift from the sail ski sled works very well even on deep snow. Skates work best on smooth ice, but few cms of snow do not stop them either.
In ski sleds wide ones are the best. If you are looking for high class carbon you can ask Airice Oy for an offer (www.airice.fi/carbon/valmistus/), but here are main dimensions for an own construction. When you start making your first sled, do not waste too much time on angle adjustment or glossy finnish - 20 degree tilt and 2 cm front end opening will be enough for most of the sailing conditions. You can also ask for WIIMA hinges with four or five predefined position angles and put them to a simple plywood deck. Main dimensions are same as in the instruction above. Rear ends of the skis are to be put 75 cm from the rear hinges on soft and 95 cm on hard snow surface.
In the times before Vadim Volotskoi came up with his wide MUST sleds the narrow ones were the best. The most successfull was Black Cat developed by Arto Ravander, SAVO is a kind of "copy cat", but it also works fine. Here is the instruction:SAVOkelkka.pdf Take your time to read about waxing the skis!
Even faster are three skated sleds - very popular in Poland these sleds offer excellent course race capabilities on larger flat ice surfaces. They use the same skates as DN class, so this part has experience all the way from 1929