There are a few different ways to steam tamales without a steamer. Read my blog post for more options
Place the vegetable steaming basket in the pot.
Pour in water but don't let it reach the top of the vegetables steamer basket. The tamales shouldn't touch water underneath!
Line the vegetable basket with hydrated corn husks.
Now add the wrapped tamales into the pot. Don't overcrowd them or squeeze them in.
Now you're ready to steam the tamales as usual.