What's the best application to create our own custom watch faces?

What’s the best application to create our own custom watch faces?

There is no “app”, you have to code the watchface in Android SDK.
https://plus.google.com/u/0/112987136604474725579/posts/A43cLuUBfji
Different way as on W806/W812/W815

Is there a way to convert a watchface .zip file to apk?

@Bernard_Sayes
No, you can use parts of the watchface from Android Wear (e.g. Pointer, Watchface). But you have to compile a APK out of it.

@Ken_Williams
I don’t know if the Q1 supports watchfaces as the D5 does. And you can’t convert APK (only working on KW88) to Zip. Either you have to code a watchface as APK or by clockmaker (ZIP). You can however simply unzip the APK und use the included PNG.