They're both correct, but the grammar is different:

"I practised speaking English yesterday."

I practised speaking [English]

This tells us what you practised doing yesterday. 'Speaking' is a verb (gerund form), and it tells us what the activity was that you practised. The object is just 'English'.

"I practised spoken English yesterday".

I practised [spoken English]

In this sentence, the only verb is 'practised'. The object is 'spoken English'. The word 'spoken' is a past participle working as an adjective, and it's describing 'English'. The noun phrase 'spoken English' tells us what kind of English you practised yesterday: you practised 'spoken English' as opposed to 'written English', for example.

I hope that makes sense.

They are both fine. The first one sounds more natural like something you would say in a conversation. The second one sounds more formal in an educational context to the point that it sounds odd.

John spoken works there grammatically as a participial adjective. It emphasizes the difference between written English and spoken English for example. More common participial adjectives are things like “The fallen leaves ...”

Hello Amy, I practiced spoken English yesterday. This is correct.

thanks all of you 😬

I practiced speaking English yesterday.

Spoken is the past participle of to speak, you could not have spoken or practised your speaking of English the day before yesterday when you practised speaking your spoken English yesterday.

Now your speaking has become spoken.

Do not confuse the adjective spoken with the past particle of to speak [spoken]. past participle

"A softly spoken man" "a blunt rude spoken/or speaking man" are not what we are discussing here.