This type of leather craft is often used to make knife sheaths, belt slides etc. Vegetable tanned leather is easy to form.
When the leather is soaked in hot water (hottest from the tap), it is easy to shape over an object. When soaked in hot water the leather is almost as smooth as a chamois, and once it dries it will retain its shape.
As a base to form it is best to use a plywood board, on which you can contain the leather by stapling or nailing. You can fix the object over which you want to shape the leather by using double sided tape to make it stick to the plywood board. During the shaping process you have to replace the staples of nails for a tight result. So keep a clawtool at hand.
Note: Leather will shrink! Make sure that the leather is still secured with staples or nails during the drying process. The leather shrinkage can be an advantage. For instance when you make a cover for a pocket knife, this knife will remain in the leather cover because of that shrinkage even when you hold the cover upside-down. The knife is easy to get out, but will not fall out by itself.
Tip: Making a clean, sharp angle is difficult. To keep these sharp corners in place use a hair dryer to speed up the drying process of the leather. Remove the staples or nails when the leather is dry.
Have fun!