Before anyone can become a domain flipper particularly if it is for the expired domains then there is a need to understand the domain expiration process.
A registered domain has an expiration date and once this date comes and the domain name is not renewed then the domain name will be put in a status: REGISTRAR-HOLD typicall for 30 to 45 days depending on type of TLD.
After this 30 to 45 days, the registrar may place the domain to pre-release or may file a deletion request. When the registrar place the domain to pre-release, the domain name is put to auction to sell to the highest bidder. When the registrar file a deletion request the status of the domain is change to REDEMPTIONPERIOD for a maximum of 30 days.
When this pre-release is over and no one bids to the domain or when the REDEMPTIONPERIOD is over and the owner did not initiate a renewal then the domain name will be place in the PENDINGDELETE status for 5 days.
After the PENDINGDELETE period is over the domain is completely drop and is publicly available.
Once the domain is completely drop it can be acquired by engaging the Automated Registration Software (ARS) Backorder services or by manual registration. Note that in the case of “highly in-demand expired domain” the manual registration approach has a very slim chance to get it as compare to ARS backorder services.