In my craft, I work with a lot of figures such as dolls and poppets. I find them to be particularily effective in Sabbat focused rituals and spells. Since Mabon is all about the harvest, a scarecrow is the perfect vessel for this time of year.
This doll will be tasked with protecting whatever it is that you are currently "harvesting."
Twigs or sticks: Choose your type based on the properties you'd like to instill in the doll. I actually took mine from one of my besoms so that it would be extra protective.
Clay: The head of my scarecrow is crafted from clay which represents the earth and everything that it grows and sustains.
Strips of cloth: Though your scarecrow doesn't need clothes, I recommend you make them something. Clothes are part of what brings the spirit of the scarecrow to life. I gave mine a hood because of the ceremonial aspect tied to these garments.
Twine: This is just to hold everything together. I like how twine looks, but you could also incorporate coloured threads for different properties.
Tea/herbal mixture: I soak my strips of cloth in black tea for physical energy and graveyard dirt for protection. Tea is also the second most consumed beverage on earth, which makes it a great link to creating a "human-like" figure.
Optional: harvest plants and foods (these can just give a little boost to the working).
Craft your scarecrow as you see fit and then tell it what harvest/crop it is meant to protect. Once Samhain hits, you can bury it. You can also keep it in your home after, but let it know it's job has finished and it is welcome to rest going forward.
You may find it helpful to speak to your scarecrow periodically to help keep it focused.