Use 2 big item to hold liquid. Kreg is too much (and too hard to get) but if you get RV kitchen you can get the tank for car; so you can upgrade it to a bigger one, with crafting skill.
Then assign the empty item to a letter near (a) and quickly spam the letters in the good order . Like (-)recraft - (i)tem that hold water.
After this put water into your tank etc.
In the early game I tend to end up with loads of invididual plastic bottles to purify, and aside from the underlying hassle, the inventory system messes up assigning letters to the containers about 1 time in 3, and I have to go in and manually re-assign them before I can continue.
There’s actually a nice way to really speed this up. If you go into the controls and scroll down a little while you will find an unbound command called “craft as long as possible”. If you bind that to a key (I use ‘’ myself) then you can simply hit that key, order to clean water, and the game will stay at the “select container screen” for as long as the fire lasts, allowing you to just hold the key for whatever item you want to store the water in and quickly purify all of the water.