By all means try the two sheets of glass and sun / oven approach if you think you can make it work: the theory suggests it's a winner and I really wish you well with it.
I tried it (gentle oven method) and once released from the glass sandwich had a minimal improvement in the flatness - if at all. What I did get was a horrible glaze across the areas where the glass touched the record surface suggesting a flattening and distortion of the groove peaks - and I'd taken hours running it up to temperature and allowing it to gently cool. This was on an LP that now sells on ebay for eye watering amounts of money that I'd had from new. What did an album cost in 1973?
In a recent thread this advice was offered by Alfonzo "I have just had some warped unplayable lps flattened by analogue seduction for about £4 per lp plus post and in all cases they are now playable". This seems a much safer approach to me.
If only I'd known at the time.
Source: Orbe SE / SME IV / Cadenza Bronze
Source: WD NAS / Cyrus Stream X2 / Chord DAVE
Source: Oppo UDP-205 (CD/DVD-A/SACD)
Amplification: Icon Audio PS 3 Sig Phono + Audio Research LS27 + Musical Fidelity A5cr Power Amp
Loudspeakers: ProAc Response D28
Cables/stands: Mark Grant G1500HD + Linn K20 + Cat 5e
Other bits: Okki Nokki keeping things clean