I was very keen on this idea, and made a bed 7m X 1.5m on my allotment (a rough meadow full of the usual perennial weeds and not dug for years), and I have to admit I half killed myself dragging sacks of stuff from the car park to allotment, and heaving them in and out of the car. Spent a lot of money as well.
I came to the conclusion that very strong fit people, or those with tractors and unlimited access to stables, cowsheds and all sorts of layering materials, could make lasagna gardens very easily - but I have reverted to digging as being less exhausting. My one bed proved very fertile, and the weeds were successfully stifled, but I just haven't enough stuff to keep piling on top of it.
I am compromising at the moment by scraping layers of grass and weeds off my newest bed while digging it out, and stacking bags of them over cardboard/tarpaulin on a second 7m "lasagna" bed. When the bags are rotted down, I will remove the tarpaulin, put down more cardboard if necessary, and tip out all the bags on top to make a second "instant" bed.
Last year I bought 4 tomato bags, laid them out on cardboard/newspaper, attempted to grow tomatoes in them (blight struck) then tipped out the contents to make a rather shallow instant small bed. I'll do that again shortly, as it is a good way of smothering the weeds and getting something growing at the same time.
