The purpose of the cardboard is to block sprouting weeds ... a few layers of dead leaves and other compost materials under it would not change the results.

In the spring, just dig small holes to transplant your seedlings.

I would not sheet compost on top of cardboard since that leaves the compost material up where critters that I would not want messing around free to do that.
Everything I have ever read about sheet composting indicates the material should be buryed in the soil, covered by several inches of soil. I have yet to see anything, from those that have studied this, to suggest putting the material on top of the soil.

Maybe I should have said Lasagna garden instead of sheet composting.

The thing with cardboard is that, it is almost all carbon! The reason you really want to put it at the bottom, is that you want to use it to absorb the nitrogen leached from the material in the pile above it, thus reduce wastage of N. Just a logical guess, no?

OP plan works. I've done it many times.

In our rainy season it keeps moist just fine. In other seasons I've used burlap or an old tarp. Use what you have. When I lifted the burlap to check on it there where countless worms. In spring there were few worms left probably because they had consumed all the organic matter.

In spring just insert trowel & pull back to plant small perennials.

Lasagna Gardening is just strange. Why not work with the native soil?

I have yet to see any Commercial operations using Lasagna layering, no room for profit after all that labor.

I could be very wrong, but it is not conventional at all. Just like the saying goes- "farming the land"

Lasagna gardening is composting in place. It might be strange to you but it makes perfect sense to a lot of people.

As for working the native soil and using conventional "farming the land" methods... the U.S. Composting Council's statement on the 2012 Farming Bill has some pretty compelling arguments against conventional farming methods.

"The U.S. is losing topsoil at an alarming rate, not only from wind and water erosion, but also through farming practices that rob the soil of organic matter. Traditional farming tends to dry out the soil, deplete nutrients over time and cause soil erosion."

Other studies are showing that the vegetables we eat today are less nutritious than the vegetables we ate 20 years ago. That is the result of conventional farming methods.

We are not putting back what we take out of the soil. We throw our food waste in landfills instead of back into the soil.

Composting is crucial to sustaining life on this planet. Whatever strange method we use.

Here is a link that might be useful: USCC Position on Farm Bill 2012

O I thought it was not using the native soil at all.

I lay dead leaves in an area, year later the soil is rich, and drains very well. Would this be "lasagna gardening"- if that is what you consider lasagna gardeing-composting in place..

From my perspective, lasagna has some special advantages.

First, for a new garden in soil that is very poor in texture and/or nutrients, lasagna offers a way to grow something without trying to till organic matter a foot deep right away. You can simply dig up a few inches of soil and layer it in between organic matter layers. While deep tilling may provide a similar result, this is much less work, at least on a small garden scale (not tractor-sized).

Second, you don't have to have compost, you can start with ingredients and compost them in place. Labor and time of handling materials both saved.

Third, the decomposition process itself appears to provide a highly active and enriched environment for plant growth, due to the high microbe and nutrient levels.

I don't know if people do it continuously or whether it's more of a startup method for poor soil until it's more improved.

I did it once with a small bed in poor clay converted from lawn, and was impressed with the results. Is it viable for a farm? Maybe not. As long as it works, you can call me strange all day long. :-D