Here is an adze that I made and served as my main seat carving tool for years. The wood is from a tree trunk and branch. I've found that the branch (handle) should be about 60 degrees off the flat of the blade. As you can see, I had to insert a wood stop block after the integral block broke off (after about 100 chairs).
In response to a recent question, I've made a video of attaching the blade to the handle. I use artificial sinew or waxed cord. The process begins with placing a loop of sinew on top of the blade and then wrapping it around the head and blade until only the end of the loop is exposed. Then you feed the end of the string through the loop and pull it under the wrapping. It has always amazed me how tight this method holds the blade, and for years. Thanks to my intrepid apprentice and cameraman Josh King.