I made this piece about twenty years ago, when I took a short series of night classes on fabric crafts. At roughly a foot tall, it was a planning piece for a much larger piece which has, unfortunately, since disappeared in a house-move.
Unfortunately, that's well before Instructables began, and about 8 years before I started digital photography, so all I can show you are these "finished" images.
I made the felt from fleece, washing it in soapy water, and then rolling it briskly in a cheap beach mat.
I drew the outline of the tree on a sheet of paper, and then sewed along the outline to transfer the design to the felt. Ripping the paper off, I then "coloured in" the tree with paired green-and-brown threads to simulate the texture and colour of a tree.
Embroidering the Sun was a lot trickier, not because of the shape, but because I was sewing into a very thin, patchy section of fleece.
I didn't use a frame or hoop, just held the felt taught by hand while I sewed. It took... hours. I forget how many, but it was a lot.
In the final piece, the Sun was not embroidered, but was a deliberately-ragged piece of thin cotton, which I painted in water-based paints than ran and merged into each other, and then appliquéd to the felt, before embroidering the tree in green-and-brown yarn.