If I or my opponent have Goodra with "Slip Trip" in play, can I still attach a Team Flare Tool to my opponent's Pokemon?
Yes. It does not prevent a player from attaching a Tool to another player's Pokemon.
Source: Phantom Forces FAQ (2014-11-13), TPCi Rules Team (2014-11-13)

Relevant cards

Note: All applicable cards may not be listed below.
XY4_77