If the sample shatters while trying to mount it to the copper blocks it could be that you should try tightening each screw a little bit at a time in a criss-cross fashion (that is, try tightening screws just a little bit at a time starting in one corner, then crossing to the furthest corner and tightening that one a little bit). It can be extremely frustrating to tighten the screws tight enough that the sample is secure, but not so tight that the substrate breaks.

Another method may be to apply a little bit of indium directly do the sample's leads (using a wooden dowel to carefully push the indium to the lead, or by using soldering techniques as in the Hall measurements) as well as to the copper blocks.

It is recommended that one should practice the procedure on an already broken or useless sample before trying on an important one.