IsIt is possible to use wood that is already covered with fungi to put into your container. From aSections of fell tree for example. Coming across already spalting wood should be just as easy. In the event you cannot get any (fungi) you can, like keshlam says, purchase spores although. Although I don't have any specific suggestions as to where to acquire them. Coming across already spalting wood should be just as easy.
There are some other suggestions such as too simply picking mushrooms. I would suggest if you are going to do that you should refer a guide that has information about mushrooms in youyour local.
Be careful not to leave the wood in too longBe careful not to leave the wood in too long as the process can penetrate the wood to the point where it is too soft to work. This is why you are checking it periodically.