I take tons of snow and pile it in a square. Then I pack that in while pressing on the sides with a sled or flat object. After that, I keep piling up snow onto the front part of the jump to make a lip, pack it in until it is solid, and let is sit for a day. After that, it will be ready and perfect to hit.
pile a ton of snow. pack it. shape it. pack it. define lip and edges. pack it. then spray water (from mouth) all over it. let it sit for at least a half hour but mainly depends on the size of the jump. then shred it.
if you can snow blocks are the way to go. build the 3 outside walls and fill it in. then build the walls up more depending on how high you want it. once youve got the generally shape start packing it all in and making it smooth. let it set for a bit then send it.
Stick your skis along with your friends' where you want the back of the jump to be, stomp out the are where you want to build the jump on. After that try to get big chunks of snow to build the outline of it and gradually fill up the gaps with soft snow. carve out the edges and stomp/pack it as much as you can and it should be pretty solid.
First, The Inrun- make sure your inrun is acceptable, make sure there is enough speed, generally you will need more speed than you think, MAKE SURE that there will be little to no compression between inrun and transition into the jump.
Second, The jump- First measure out the base with your skis, a medium park jump is about 4-5 ski lengths long and 2-3 wide, you can obviously make it as wide as you want. Dig down until you can cut some blocks of snow in an area near where the jump is but not in the base area. Cut squarish blocks so that they can be stacked as straight as possible, stack the blocks back and two side walls around the perimeter until the jump takes shape. As you construct the outer walls fill in the center with the smaller garbage blocks that are left over. Once the jump is all filled in put on a pair of skis and pack it carefully paying attention to a continuous transition. Step out the inrun nice and wide.
Last, let it sit before hitting, For best results let it sit overnight
if youre going to go this in depth then the very first thing you should do is check the landing. we built a jump earlier this year and didnt think to probe the landing until it was done. turns out there was about 16 inches on top of solid rock. a whole days worth of perfect jump building for nothing.
It obviously wouldn't work in deep backcountry (or many other situations), and it is very impractical but it works amazingly, hardens fast, and it a far better alternative than constantly icing a jump. A snowblower and plywood/OSB provide some of the best jump building I've ever seen. The snowblower removes air from the snow, so it is super dense and hardens quickly and in a way where it is stable, yet forgiving. The plywood holds the snow in place. It gets aggravating when you continually pile snow up and it seems like there is no progress because snow keeps sliding off the side. The plywood also gives the kicker nice square walls for a professional fit and finish. But it's difficult to transport this shit, so a scoop shovel is the next best option.
Side step and slip your inrun, and your speed will be great. What we normally do is pile blocks of snow, and put skis and boards around where the lip will go to define the shape. I have never tried spitting water on it, but I'll keep that in mind next powder day.
If it's a jump for a handrail, you can get some of the road salt and throw that on it. It melts and then re-freezes harder. Just make sure you layer snow on top of the salted area too. Also pack it down with skis.
As for bigger jumps, get blocks and pile them high and form a wedge. Then do other various techniques for shaping.