What you'll need: Two to three 1g or 5g buckets depending on your bags, ice (lot's), Bubble Bags, a way to agitate your water/flower/ice mixture and a spoon or other scraping device that won't damage your bags.
There are many places to obtain bubble bags. I personally use bags made for 5 gallon pales, and I use a 3 bag system: 220u/75u/25u
The largest micron bag is used to filter out the plant material. Everything that comes out of this is useless for bubble hash. If you so choose, you could try using it for edibles. I just throw mine out. The other bags are where your hash will be produced, and depending how many bags you're running and the micron size of each. Some people run a 5 bag system, others a 2 bag system and others up to a 7 bag system. it's all personal preference and what works for you.
Agitation: Budget-wise I mix mine by hand, or with a wooden spoon attached to a drill. This works perfectly fine, but my wishlist has one of these machines on it:
This is basically a washing machine for your flower. You put your product inside a mesh bag and contains your water and ice mixture. It will agitate automatically and makes draining easy with a release tube you feed into your buckets through your screens. Excellent product, but also quite expensive for a DIY set-up.
The steps are the same weather or not you use the machine. The machine just requires you turn it on/off and drain as opposed to mixing by hand and dumping buckets.
Fill a bucket about halfway with ice and add your water to your desired level.
Next you will want to start your agitation, and continue doing so for apx 3-5 minutes. You want to separate the trichome heads from the plant material and preferably not blend the slurry which will cause more plant material in your finished product.
Set-up your bags in your next bucket starting with your largest micron size at the top, working your way down to the smallest. Dump your water/ice/flower mixture into the bagged bucket and let settle for apx 5 minutes. You're wanting the trichomes that fell off to get down through your screens.
Next, pull your largest micron bag with all the material out of the bucket and put aside, or whatever you plan to do with it. Some people like to do a second run to make sure they got everything useful.
Pull the sides of your next bag down the edge of the bucket so you make a tight surface at the opening. this is where you will scrape with a spoon, or other material and start scraping. I use thick cardboard for mine to rest on as it pulls the water from the material. other's use parchment and other's blot with a separate screen.
Continue until all your hash is scraped off and move on to the next bag. Rinse the bags starting from the edge to centre to get anything you may have missed. Repeat all steps if desired.
Drying: Another personal preference. I freeze mine and use a micro-plane over cardboard and let sit for apx 1 week. Some people will chop it up as fine as possible and put in a cupboard. You want to get all that moisture out or you will end up with moldy product.
Once you make this once or twice, it will get easier. The first couple of tries will be a learning experience, and will always be as you make more but will come easier to you.
This is just a guide, and the way I make this product. This is in no way the only method, but one of many.