The fully-approved EASA B1 course is a minimum of 2,400 hours and comprises 3 important elements, each of which must be offered as an integral element of the course to keep it as a fully-approved course.
There are the Module examinations and classroom work leading up to them, the Practical Training carried out in an approved Training Workshop with assessments sigend off by approved assessors, and the OJT which must be done in a Part 145 MRO and is structured, proper training under an instructor and assessor. All these elements must be provided by the same Part 147 school as part of the same course.
The outcome of an approved course is a Basic Training Certificate. What's needed now is a minimum of 2 years relevant work experience before a licence application will be considered.
For those who decide to work for their licences by another route, the Practical and OJT are replaced by a requirement for a minimum of 5 years relevant work experience, with records evidencing that they have acquired the necessary skills and experience to be considered for a licence once they have passed all the Module exams.
There are, of course, variations on the above; certtain kinds of prior experience can be counted toward the work experience, for example. But that is a broad outline of how it works.
What is not always understood is that a EASA B1 course without the OJT cannot be an approved course, no matter how long it lasts.
Finding "OJT" somewhere else is pointless; the course is still not approved and therefore the student still has to do the 5 years work experience.
That's my understanding, and I'm well prepared for someone to come in who knows more, to prove me wrong!