Have you researched basic flux research and can therefore make alembics? If you have that done make 4 alembics. If not you will need the research first. It becomes available after warded jars (which are not absolutely necessary).
You don't pipe aspects or the seemingly liquid essentia, you just plonk the alembics onto the crucible. You can have a maximum of 4 on one crucible and each one holds 16 units of a single aspect.
When you craft something and there are extra aspects they go into the alembics if there is room for them. The essentia will stay in the alembics until you take it out by using glass phials which require multiples of 8 or you can use it for crafting with the infusion altar or by using a wand on the alembic you put it back into the crucible when it is boiling. Shift-clicking the alembic with a wand will spill the essentia out into the aura.
The way to make sure you don't spill aspects is to always try and use items that have exactly what you need and nothing else. If there are extra aspects try to make the amount a multiple of 8 but not go over so much that it would spill. You can have the same aspect in more than one alembic.
A big help in this work is the tallow golem, be sure to research and make one asap. You only need one and you right click with it on an alembic and he will take the essentia out for you. You need a chest nearby with glass phials in and have it touching a marker. Filled phials go in the chest or if you have warded jars marked similarly the golem will fill those first.