I used to follow this in my earlier version of PCS7 ( V7.1 and before ). Just tried with V8.0 and seems to work good.
1) Open @pcs7typicals from the graphic designer
2) copy one of the block icons and you edit it by deleting fields which are not necessary for your created FB and like wise you can fields as required for your blocks.
3) Once your FB editing is done, dont forget to make these changes --> a) blockicon--> properties--> system-->type ( should be same as your block name in cfc) , b) blockicon --> properties --> system-->servername (same as that of userdefined faceplate ).
Hope this helps.