Yes quite easy
Take a big pan of water (with a lid) and add your scraps. Hides, sinew, fish air bladders etc...Slowly raise the temperature to no more than 65 deg celcius. This is key do not let your water get over this temperature. You will still get glue but it won't be as strong. Too high a temperature will break down the collagen instead of 'releasing' it. Keep it at this temp for 8 hours.
Then strain the mix to remove any lumps/pieces left. Keep these as you can do a second cooking.
Now gradually reduce the mixture to a thicker consistancy. Lid off the pan - still not going over 65 degs.
Once it has got thicker you need some baking trays and parchement paper to line them.
Pour your glue over the trays until it is about 1/4" thick.
Let it cool and gel.
Once gelled you can cut it into small cubes.
Now take a fan and blow air over your glue cubes until they have dried and are completely hard all the way through.
You can skip the drying process if you are willing to freeze your gelled glue. This way is nice as you simply unfreeze , warm up and it is ready to go. The dried cubes need soaking in water until they go soft before heating them.
Good hide glue is amazing stuff.