For PXE, you need to add in dhcpd something like:

option domain-name "bitslack.local";
allow bootp;
filename "/pxelinux.0";

pxelinux.0  is present in pxe.tgz and is taken from Slackware PXE package.
There are also some config files in pxe.tgz you can use or modify as needed.

All of them must be available via tftp.
tftp-hpa is available in slackware and work well.
I have this in inetd.conf:

tftp  dgram   udp     wait    root    /usr/sbin/in.tftpd  in.tftpd -s /tftpboot -r blksize