Qualifying Work Experience, QWE, is a separate requirement from the SQE1 and SQE2 assessments themselves. Most SQE candidates need two years of it, full time or the equivalent, before admission as a solicitor of England and Wales, on top of passing the exams. Qualified lawyers are the exception. The SRA says that, unlike other SQE candidates, qualified lawyers do not need two years' QWE at all. That covers lawyers with practising rights in another country, and some UK-qualified lawyers too, so check the SRA's qualified lawyers page if you hold any professional legal qualification.
For everyone else, QWE is more flexible than many people expect. It can be gained in up to four different organisations, in paid or voluntary work, in England and Wales or overseas, and it does not need to cover English and Welsh law. You can gain it before, during or after you sit the SQE, so there is no need to wait for your results before you start.
The confirmation has to come from a solicitor of England and Wales or a compliance officer for legal practice, COLP. They are not re marking anyone's legal knowledge. They are checking the existing experience against the SRA's QWE competencies and signing off that it covers what is expected.
If you are not sure whether you count as a qualified lawyer, check before you start collecting evidence. The SRA's qualified lawyers page sets out who counts.
This is a separate question from the SQE2 exemption, which removes an exam rather than a work experience requirement. Not needing QWE and being exempt from SQE2 are decided separately, so check each on its own terms rather than assuming one covers the other.
Finding a solicitor willing to confirm existing experience is often the hardest part in practice, particularly without an existing contact at an English firm. A number of services exist specifically to review evidence and sign off QWE confirmations for a fee, since this gap comes up often enough for overseas candidates that it has become its own small industry. It is worth researching and checking reviews carefully before paying anyone for this.