Unfortunately not all sources or packages do contain DESTDIR or INSTALL_ROOT, this what makes it harder to install things. If I do prefix=SOMEWHERE during configuration instead of doing prefix=/usr, some projects like vim, for example, attaches SOMEWHERE as the path to the scriptnames once it is make install.
Also some projects gets broken, either because their search path started with SOMEWHERE which come from the configuration prefix or It does not work at all.
Fortunately there is a tool called src2pkg, and this is what I used for creating slackware packages *.txz.
The option -DESTDIR and -JAIL is what I always used when using src2pkg. Now I am curious how -JAIL work. There is an option called -A where it says that it will generated a script once compilation is successfuly...? But I never used that -A option.
So how does -JAIL option work at all?

I do not want to created a chroot just to make install, nor src2pkg setup chroot at all? Does it?
