I know there is already a dozen of these most likely already on here but I made this for my girlfriend after seeing the movie and I think it turned out pretty good. These steps can be applied to sculpt a multitude of various things.
If you have any questions feel free to comment or send me a personal message.
Step 1: Framing
To begin making your very own Groot begin by creating the framework. To do so cut a piece of .25" aluminum rod to length. Then take the piece you cut of and bend it to the general shape you want the finished piece to be displayed in. Next take some one .125 or smaller rod/wire and make the arms by wrapping it around the .25" rod and securing it with 28 gauge wire. Bend the arms to the general shape you want them displayed in.
Step 2: Initial Layering
To get the figure to take shape you'll add layers of apoxie sculpt adding volume and texture as you go. To start off though, add aluminum foil. This will save you having to add more of the pricey apoxie than you absolutely need. Once your happy with the base foil, add a layer of the apoxie sculpt to get the general shape refined. I embedded small beads to use as eyes but really you could sculpt your own or use anything small and spherical.
Step 3: Detailing
Once that sets up add more thin layers adding texture as you go. The easiest way to add texture to things is use the objects your trying to emulate. So since I'm trying simulate wood I went outside and found a piece of bark to use as my sculpting tool. Contining to add more material while shaping using the bark refine the details.
Step 4: Painting
Coat the entire figure in a brown paint this can be spray paint, brush on acrylic, and any type of paint really. Once that dries coat it with a clear lacquer to seal it. The brush on watered down acrylic paint into the books and crevices and wipe away excess. This adds depth to the piece by highlighting the detail.
Step 5: Final Details
Place into a pot with foam to hold it in place. Add some moss to cover the base, and place some sporadically all over.