When not cleared straight in for a VOR approach, how is this type of procedure executed?
When talking about approaches, you should limit your terminology to mean the same thing for you as it does for ATC. In other words, for a Category A aircraft:

ATC would not clear you for a Straight-in Approach unless you were inbound from the South for Runway 36 or inbound from the North for Runway 18. There are no Straight-in minimums for this approach, only circling minimums. To use this approach, you are required to fly a modified Traffic Pattern no lower than 1760 feet MSL until you reach a point where you can descend safely to the runway while maintaining cloud clearance. ATC will give you instructions on which direction to circle. In the absence of instructions, circle in the direction prescribed for Traffic Patterns in the US Chart Supplement and Sectional.
There is no Back-Course for a VOR. A Back-Course implies an ILS or Localizer transmitter. VORs transmit their navigation signals differently than ILSs and Localizers. There are Radials for each VOR dependent on your bearing from it. There are To-indications and From-indications for each Radial depending on your location on the extended Radial relative to the VOR. There is normal/direct-sensing and reverse-sensing for each Indication dependent on your Heading.
If you were flying inbound direct to the GDM VOR on the 097° Radial, you are East of the VOR flying Westbound on a heading of 277° Magnetic. The safe altitude at which to remain above is the Minimum Sector Altitude of 3300 feet MSL unless assigned otherwise.
You may request from ATC a Hold at the VOR to buy time to prepare for the approach or to lose altitude. Although, it is not part of the official Instrument Approach Procedure until the Missed Approach Procedure, you may use it to get established inbound to the airport or VOR on the 277° Radial instead with ATC clearance.
If you are not cleared for the hold, or accept clearance for the full procedure, once you pass the VOR, you may descend down to an altitude at or above 3000 feet MSL as long as you remain on the 277° Radial.
You may perform a Procedure Turn (starting with a left turn to a Heading of 232° Magnetic for 1 minute, then a right turn to 052° until reestablished back on the original Radial) anywhere along the 277° Radial as long as your aircraft remains within a 10 Nautical Mile distance from the VOR during the entire procedure. The general convention is to travel at least 2 miles or 2 minutes before starting the Procedure Turn.
Once you are established inbound on the 277° Radial with a Course and Ground Track of 097°, you may descend down to, but no lower than, 2400 feet MSL until you reach the Final Approach Fix which is the GDM VOR. Please be cognizant of the fact that when ATC Radar services are unavailable, other aircraft may be holding at the GDM VOR at or above 3000 feet MSL. It would behoove you to cross GDM inbound below 3000 feet MSL.
Once you have passed the Final Approach Fix, you may descend down to, but no lower than, 1760 feet MSL to start your Circling Approach. The Circling Approach May only be started if you have established visual contact with the runway.
If you never establish or are unable to maintain visual contact with the runway environment during the entire Circling Approach, remain on or return to the 097-From/277-To Radial until you reach the Missed Approach Point of 1.9 miles DME from the VOR (1 minute, 54 seconds at 60 knots ground speed). If you still have not established visual contact, perform the Missed Approach Procedure (a climbing left turn to circle back to the GDM VOR, climbing to hold at GDM at an altitude of 3000 feet MSL).
If, at any time during your descent past the Missed Approach Point, you can not maintain cloud clearance, circle back over the runway to join the Missed Approach Procedure.

—————————————————————————————————
Per the OP’s edit:

Remain at or above the MSA for the inbound heading from which you are coming or your assigned altitude.
Do not descend until you have crossed GDM on an outbound leg.
Once you have crossed GDM, utilize the hold to descend down to but not below 3000 feet MSL.
Notify ATC on whether you will proceed in on the inbound leg directly from the hold, or do the full procedure outbound to the Procedure Turn.
If no altitude loss is necessary, notify ATC of your request to proceed inbound on the procedure. You will have more than 1.9 miles to descend down to 1760 feet MSL (depending on where you get established on the Initial Approach course/leg).
Alternatively, you can intercept the procedure anywhere on the Initial Approach course/leg if cleared by ATC. Provided you do not start your descent to 3000 feet MSL until you are established on the procedure outbound or to 2400 feet MSL until you are established on the procedure inbound. Either inbound or outbound legs must be within 10 NM of GDM.