I use a 40gal poly water trough. I have several of them for the goats, chickens, geese etc so I can usually find one not in use to brood in. They only cost about 30$ and are great for about the first three weeks. Then the little chicks are jumping up on the lip to roost and get out. Same deal though, rounded, so none suffocate.
I have a big 4x8' area built on the side of the goat barn that looks like a chest freezer that I move them into at about 3 weeks or so. There is enough room in there for probably 80 birds at that age. I have 30 in there right now. I have food and water up on wire, a small roost and a heat lamp in there. There is also a door on the front (in addition to the hinged top) that I can open and let them come out if they want. It is an ideal situation for them and they'll be out there until it is time to let them get to know the rest of the flock after several more weeks of brooding.