You can make them different ways. I chose to just line my pot w/the batting inside. Some people cram it full. The pot has a hole in the bottom. When the pot start to overflow due to crud buildup in batting you need to take it out and hose it all off and then put it back and keep doing till your pond is of the clarity you wish.
I found hanging it on a piece of old metal fencing stabbed in the ground worked pretty good for hosing it off.
You can use a milk crate or anything similar w/holes.
I have switched now to using this Matala media in mine now as it does not plug up as fast as the batting and I don't need it that clear anymore.
I use the green in winter as the black plugs up faster and I just want a long lasting flow thing going on in winter so no cleaning in the cold weather. I have in the pond all the time.
Actually this winter I just took out all the Matala media and am using the screen by itself as not much gunk anymore.
Bought this large plant basket. Lined it w/ fiberglass screen door material from H-depot or Lowes.
Stuck that basket in a nice big plant pot w/holes in bottom. Then started adding the Matala media. I put a circle of it on the bottom and then lined the sides only and stuck a hard plastic paver I had on top to hide the insides, oh and stuck a rock on the bottom of that bottom circle piece to hold the pot from falling into the pond if any wind should come around. Stuck the hose from my pump that lays on the bottom or on the shelf of the pond and the pump sucks up the water and runs it through the hose to the pot where all the gunk collects. Cleaning this set up is much easier than clean all that batting but if you have really fine particles that you are trying to collect, then the batting works best.
Water comes slowly out of pot at bottom. My pump is only a smaller one so as not to push too much water at one time. Can't remember how many gph the little pump is and I think it is a Pondmaster pump.
You'll have to clear your pump once in awhile to clear the input.
I have the perfect little picker tool to clear it out when I pull of the end screen thingy from the pump. Digs out the crud from inside the pump inlet great!