Step 1: Draw the frame of the hand. Depending on the pose and view angle, the shape of frame is flexible changed, but normally it will be a little bit flat or rounded like this :). Draw the wrist.
Step 2: Sketch the position of each finger. In this step, finger joints are represented by small circles. Connect the joints by some straight lines UwU
Step 3: "Add flesh" to the initial sketch in step 2. Note that for the female character's hand, it is recommended to draw curved lines to make the hand look soft, and for the male character, you can draw the hands slightly rough.
Step 4: Hide the sketch layer / erase the sketch, leaving only the "flesh" part =)
Tada, here's the result. It is very simple, isn't it? Let's see one more example for better understand.
That's it UwU. Do similarly with the other poses in the first picture, and try some more exercises below if you like.
Good luck to everyone UwU