i have one similar to that. a male that was sold to me as a "burmese birdeater" (Chilobrachys burmensis??) died of old age. i stretched him out on some cotton, sprayed him with some glosscoat, and stuck him in a frame. sounds kind of redneck, but it worked. year and a half later and hes still well preserved.
Another way to do it is to get a goldfish bowl and fill it halfway with some sort of lacquer or gelatin or soemthing that hardens clear, and then putting the tarantula in and then filling it the rest of the way. My friend has done this and it looks nice.