normally I brood in a large wooden box, but they got too big, and it is too cold in coop- and too far for extention cord, so I put the chicks in a shed, then in a 3x4'x4' tub I have on loan from my hardware store. seems to work well. . it is holding temp of 80 under lamp, chicks are 4-6 weeks old.
My brooder was a large, plastic laundry basket with cardboard boxes around the sides so that they couldn't jump out, and a heat lamp suspended overhead. Sorry it seems that this photo was taken vertically and the website is turning it back on it's side. You cannot see the laundry basket very well in either photo, but it is the black basket-y thing that you see wherever the cardboard isn't blocking it.
Here's one of mine, currently in use, of course It's not pretty, but it sure is functional! I think its somewhere around 3W x 3H x 5L, something like that. My husband built it out of scraps we just had lying around, so the price was right too! This thing sees a ton of use, I brood in it all year round. I just change the bulb in the heat lamp depending on what the weather is like. I sits on a couple of pallets that are sitting on 4 cinder blocks. Before this thing, I was using a modified Rubbermaid tote, inside my house. I'd have to clean that tote out everyday, NEVER again! I have another brooder about the same size, its a little prettier, but I mostly use it for older chicks that don't require heat or birds I have for sale. It's a little further away from the house and I'd have to run an extension cord to it for little babies. The one pictured is definitely my "go to" brooder!
Good job everyone! I switched back to a wood brooder, made from an old dresser. drawers out clamp lamp. the tub was a loaner and in a month when we have snow I didn't want to fight it to return. this will be good for growing up large enough to put in pen with other hens. funny to say we will have snow in a month when it is 90 outside today.
Here is an in-progress shot of my new brooder. It is made of reclaimed pallet wood and the bottom and lower sides are lined with coroplast to make it easier to clean. (The coroplast was lining some of the pallets before they were dismantled.) I'm waiting on a thermostat I ordered and then I'll be wiring the heat lamp at one end and building the lid to prevent escapes. I also want to make a solid axle for the wheels as I am worried that simply bolting them to the legs like the current configuration is going to break the legs eventually.