The process by which Lee Harvey Oswald obtained the job at the Texas School Book Depository (TSBD) is well-known: It's part of the historical record of the assassination of President John F. Kennedy.
The first week in October 1963, Ruth Paine and Marina Oswald went next-door to have coffee with a neighbor, Mrs Roberts. Another neighbor from "across the street", Linnie Mae Randle joined the party.
The subject of Marina Oswald's plight came up in conversation. She was 8+ months pregnant and her husband Lee Oswald was unemployed and needed work. Mrs Randle explained that her brother, Buell Frasier, had found work at the Texas School Book Depository and that "they might be still hiring". Mrs Paine phoned the TSBD and spoke to the manager Roy Truly. There was a temporary position available as an order-filler.
When Lee Oswald telephoned the Paine residence that evening, he was told about the job opportunity. He went for an interview with Mr Truly, the next day, and got the job at the TSBD.
The circumstances of Lee Harvey Oswald getting a job at a building on the route of President Kennedy's motorcade (5 weeks later) was just happenstance. The idea that plotters in a conspiracy had him "placed" at the TSBD is impossible. No "placement" means no "plot". There was no conspiracy. If Mrs Randle decides to stay home or go somewhere else instead of across the street to Mrs Roberts house for coffee: Lee Oswald never learns about the job at the TSBD. He never gets a job there and is never in a position to assassinate President Kennedy at 12:30 PM (CST), 22 November 1963.
That's why I say: "No coffee for Randle, no job for Oswald -- at the Texas School Book Depository".