Using Calculate Linux Scratch 17.12.2 x86_64 iso image.
X server doesn’t work out of the box.
startx fails because Xlog complains twm, xclock and xterm cannot be found by the X server.
After some messing around, I discovered xterm has to be installed for the X server to work. After installing it, startx brings up the X server with twm (even though twm is not installed, it must be part of the X server). Xlog still complains that xclock and twm cannot be found but the X server works.
xterm needs to be installed in the 64 bit Scratch iso image.