I am using quite a bit of half inch hardware cloth. I am told weasels can get through a one inch diameter opening, so half-inch should do it, with regular inspections to make sure the wire remains intact.
For brooding, I started my eleven with a 4 ft long Rubbermaid tub, about 2 feet wide and 2 feet tall (Brooder I). I covered it with hardware cloth, and set ceramic heat lamps on top. One advantage to having hardware cloth under the lamps is that if a bulb pops, fewer shards can rain down.
For bedding, I use old towels. It is a little bit of a chore, but really, not that bad. I change them about three times a day, shake the loose stuff onto the garden, rinse the crumbles off in the tub (it is winter here, otherwise I would use the hose outside), pop them into the washer (I am so grateful we have a washer!) and hang them out to dry.
At about two weeks of age, the ducklings had grown so much I decided it was time for Brooder II. It is an eight panel puppy playpen, enclosing about 16 square feet. I set it on 6 mil plastic sheets over a sheet of cardboard, then lined the interior with plastic poultry fencing because they were small enough to get out or at least get stuck between the playpen wires (which are coated). I use an old sheet as a draft guard. I can get into the brooder with them (when I change to clean towels), so that they are comfortable with me working around them and handling them. I sit with them a while, and they crawl into my lap and snuggle around me.
Brooder II should do them for a few more weeks. They have room to sleep, room to run, room to eat and drink. Should the weather remain cold, Brooder III will be eight more panels, in the basement (which has a good finished floor but remains about 50 degrees F in the winter and early spring). I will need netting or something on top to prevent cat incursions. Once the weather turns reliably (ha ha) warmer, and they are in full feather and have had a chance to harden off with outdoor time, their shelter (scheduled to be built in three weeks) should be ready for them and they for it.
The gallon-capacity waterer (which they needed at about day 10) sits on an overturned ricotta cheese tub in a large stainless steel salad bowl. That catches much of the splash, and is a little taller (they are nearing a foot tall already, at two and a half weeks old).
I have a couple of other ricotta tubs with head and should sized holes cut in the lids for face washing.
I sprinkle a little grit in with their food.