No, you won't have a booteable CD if you do it that way.
You only need disks 1 and 2 to get a fully working system, 3 and 4 are just sources for the programas included in the other two disks.
You can also use only CD 1 if you're not going to use GNOME and KDE.
I don't know what you downloaded but .iso.asc files are just signatures for the .iso files, they are not needed, same for .md5 files.
Go here: ftp://ftp.scarlet.be/pub/slackware/slackware-10.1-iso/
And get install-d1 and install-d2 .iso files.