Given enough energy and money, anything is possible. But, in a word, no. Its an art form. You would be much better off contacting Deaver. If you really know what you want, you could contact a local spring company but they probably won't know what your after, you would have to be able to tell them.
By build I assume you mean design & either adapt or have manufactured (unless you have a forge in your workshop)
In the UK there are no manufacturers like Deaver or National, there are those who make leaf springs but very few who design them. Basically they copy or modify. I was after leaf springs for my LWB SJ which I race in a UK series. The more I looked into this the more I realised that desiging leaf springs is an art. I bought the SAE manual on leaf spring design, yes I could do the math, yes I could understand the principals, however when they were talking about testing springs to failure to ensure that assumtions you have to make in the math are correct I realised I was out of my depth. I was seriously thinking of getting either Deaver or National to make me a set of springs as it would (even with the poor exchange rates & the freight costs be cheaper than making several sets to home in on the right ones). In the end I used the knowlege I had gained to decide on standard springs from another vehicle that would function correctly, cost savings were significant & the difference to the then current performance was huge.
From my own experience you cannot hope to design a leaf spring setup from scratch & get it right first time, by the time you have had a second go at it you may as well have bought the right thing first time.
As an aside I did make changes to my previous springs by swapping in (& out) leaves from other packs, even this was unsucessful, although the springs were softer, i.e. what I was trying to acheive, they would not live.
What are you trying to acheive by making the springs yourself? Muddi44 pretty much covered all the reasons why you will save time and money by having one of the spring manufacturers build them for you. Unless you have the proper equipmnet, material and knowledge then building them yourself will be a futile effort.
In So. Cal, you have Deaver and National spring to choose from. There is also Alcan Spring in Colorado who are highly recommended by some of the 7s racers who use them.