There are many ways to build an igloo. Two suggestions on how to build an igloo is to make a small entrance and to melt the dome.
How to make an igloo you need to make a small entrance because you need to keep the heat in. You need to have a small entrance so you can have a door way to the igloo. To make a igloo you need an entrance because if don't you can't get in the igloo.
How to build an igloo you would have to melt the dome. You would have to melt the dome because you need it to freeze back for more strength so you have a stronger dome. This is important because if you don't melt the dome it won't have enough strength to hold up and it will all culaps sot's why you need to melt the dome but after you melt it you need to let it freeze back up.
As you can see you need to melt the dome for more strength and you need to make a small entrance to keep heat in. Without these steps the igloo would not hold up and would not be warm.