All you need is wine corks (a lot of them) and glue gun.
The easiest to put together the Christmas tree is using corks of the same size (preferably also from the same type of wine). Luckily at work, we sell a lot of the same wine at once. The second thing you need is a glue gun with a lot of glue. In between the corks I used glue without color and for the front decorations I used glue in color.
For the bigger tree, I used a lot of different corks. I tried to combine colored corks and white ones. It was a bit of a challenge putting it all together. And it took a lot more time. But with a glass of wine, everything goes easier.
If you try to do it yourself, please send me a picture, and I will include it in my post.