One shovel at a time.
First it has to snow. And it has to stay cold long enough for you to get the igloo built. You’ll need a couple hours, and daylight, so the snow will have to last until a weekend most likely.
You take your snowshovel and pile up a bunch of snow. If it’s really deep you can just use the snow from the immediate vicinity of the igloo itself, tossing shovels-ful into a pile.
Or, if the snow is not quite that deep, say only a foot and a half deep or two feet, you’ll exhaust the vicinity of the igloo which is only a pile at this point, a pile with an igloo inside, and you’ll have to go further afield for your snow. You will shovel off the terrace and the steps and the pile you made over by the fence when you shoveled clear the driveway.
Could be this will still not suffice. You don’t want to move any snow near the hedgehog houses, because it’s probably quite peaceful under there. So you’re walking out to the street, taking a shovelful from the pile at the end of your drive way or, when that is exhausted, taking one from the pile (pretty clean) made in the street itself in front of your house by the snowplow.
And carrying the shovel-ful back to the pile, dumping it, returning to the street for another.
Shovel by shovel.
You don’t count the shovels or the trips you make. You start out doing this, but soon learn that it is not motivating. It is a trip of, what, fifteen or twenty meters one-way.
It takes hundreds of trips.
If you had known this before you started!
But luckily you didn’t, and eventually the pile is the size of an igloo.
Then you hollow it out. You think how much this would suck if it collapsed after all that work, so you leave the walls and ceiling so thick only a cat could fit inside. You tell yourself, your kid might fit. If not, you can always hollow it out a little more.
This coming weekend.