I love this topic!
Motanka comes from the Ukrainian verb to wrap/wind, which is exactly how these dolls are made. (I make them myself.) 
Some from my collection:

There is no face because according to lore, if you put a face on a doll, it can embody a soul. If it embodies a soul, it can take on the bad—not only the good—of the person. Since everyone has their good/bad moments and traits, the doll is supposed to be free of influence.
Most dolls are used for good. They are not aligned with the folk dolls in something like Voodoo where inflicting a curse or pain onto someone is believed to happen if the doll is inflicted first. For this reason, it's against tradition to cut or pierce the doll even during its creation. Doing so is believed to "cut" the intention or establish the opposite effect of what the doll is meant for. The doll is entirely made with wrapping and knotting to keep the materials in place.
Motanky (plural) use various colours and materials to represent what it's trying to influence. For example, green signifies nature and good health, since people were their own pharmacists once up on a time and used plants for healing. Reds and blacks were protection against harm. Even certain symbols embroidered onto the doll's garments meant something, the same symbols that are used on pysanky. Even other materials such as shells, coins, beads, etc. were used to decorate the doll for more influence on its intention.
Today when people make the dolls, it's encouraged to make it out of entirely natural materials so that when it does eventually break down and go back to the earth, that it will not harm the environment. A lot of pagan/Slavic customs today rely on this as one of the main ideas is to not harm the environment. Dolls made from cottons, linens, or anything else plant-based makes the doll more authentic.
I'm not a spiritual person at all. But I love tradition! I've given a few of my dolls away to friends and family as a gift, focusing on their needs at the time. One of them was to my mom, who was suffering from nightmares. I made one with black, blue, and white colours (all for protection and peace), and hid an amethyst stone in the lining of the doll's dress. I told her to set the doll near her bedside, but near a corner if possible, looking out toward the rest of the room. The doll is supposed to call on [our] ancestors to guide the doll's intention (without embodying their souls!) so that its only purpose is to send well-wishes to the intended.
You might wonder: "Did it work?" Yes and no. Mom likely had a sense of mind of matter, knowing the doll was there. Her mind assumed the protection was there, and just before falling asleep, looked for it and her brain did the rest. But over time she stopped looking at it, and I she told me her nightmares were acting up again. Psychology might play a part here. They can work if we think they work. If she's forgotten that the doll is sitting there, can we blame the doll for not working? 