Materials required :  Wool, Soapy water ( mixture of soap powder and hot water )

This process of making felt balls is for only small volume of felt balls. For bigger volume we need more materials. This is just the basic idea and process.
First get a small jug / tub / bowl. Then make the mixture of hot water and soap powder. Do not add too much soap powder. Just make the water soapy.
Then get the wool, tear down small pieces of wool and make small puffs of wool in roundish shape. You can make the sizes of puff to your desired one. 2 - 2.5 cm are the standard sizes.

After making the puffs of wool, dip the puff into the soapy water and start giving round shape to your ball by rolling the dipped puff with the help of your palms. Keep rolling it round until you get a perfectly round and dense felt ball. You can feel the ball getting denser as you keep rolling. But do no give more  pressure while rolling. Keep it normal. 

Finally, rinse the ball out of the water carefully and let it dry. Normally it needs complete one day to get completely dry.

You are done now !

 The process is pretty simple and easy. You can get it easily done. Give it a try and make your felt balls. Good Luck