For the step prior to make your pack, you need to equalize ( balance ) all cells to the same level.
As well, all packs and cells have not the same state of charge so you need to bring all them to the same BEFORE to parallel your cell in the build
What you need is to ensure that all the cells you will parallel to equalize ( balance) need to have max 300mV from the lowest to the highest cells BEFORE TO PARALLEL
So since many cells will have higher voltage difference than 300mV, let say one of the cell have 3.4 and the other have 4.0.. so you can not parallel them from now. just follow the next step and you will be able then to parallel all them
What I suggest is to make few different groups of voltage ranges. Let say you make a group for the cell from 2.5 to 2.8V, another for the cell at 2.8 to 3.1V, another group with cell of 3.1 to 3.4V etc.. up to 4.2V ( this step is not to make your pack but just for the equalization step!)
So instead of charging all cell individually, make these groups with all these range of cells voltage and than you can charge these group instead of charging each cells, that will save you a lot of time! so proceding to a charge of 5 or 6 groups is faster than charging 100 or 200 individual cells as well!
After all these groups are charged to 4.1V or 4.2V, the final equalizing step would be to parallel all group cells together.
One of the best way I found to parallel cells fast if to use aluminum foil sheet and some smooth packing material. What you do if to place all cells in a sandwich with one top and one bottom layer of aluminum foil sheet. It work perfectly!
But since all cells don’t have a the perfect exact lengh form each other, to ensure that all cell have a good electrical contact to the sheet you can use some soft bubble or foam sheet material to apply pressure on the foil on both top and bottom, than to use rigid material to apply uniform pressure on that sandwich. I will try to post a picture that.
( dont forget to prepare the cell nickel tab to have a good electrical contact for each cells! ( follow the way i suggested in teh thread when i flip the tab nickel sheet of the cell ends with some pliers