One way to practise your favorite first position Bb form along with the 1st pos. F form might be by playing One Morning in May in C. Here's the first two lines:

C Bb F C
One morning, one morning, one morning in May,
C Bb F G
I spied a young couple they were making their way.

F

PS Of course you can play the C and G at the 3rd fret when you like.