Begin by exporting your data from Webflow. Navigate to the Webflow Designer, and go to the "CMS Collections" section. Select the collection you wish to export, and click on the "Export" button. This will download your data in a CSV format, which is suitable for further processing.

Open the downloaded CSV file to inspect and clean the data if needed. Ensure that the data types are consistent and that there are no anomalies like missing headers or incorrect delimiters. Save any changes made to the CSV file.

Log in to your Snowflake account and set up a warehouse if you haven't already. You will also need to create a database and schema where your data will reside. Use the Snowflake UI or SQL commands to create these structures:
```sql
CREATE DATABASE webflow_data;
USE DATABASE webflow_data;
CREATE SCHEMA cms_data;
```

Based on the structure of your CSV file, create a table in Snowflake that matches the columns and data types. Use a SQL command similar to the following:
```sql
CREATE TABLE cms_data.collection (
column1_name DATA_TYPE,
column2_name DATA_TYPE,
...
);
```

Use the Snowflake web interface or a command-line tool to upload the CSV file to a Snowflake stage. A stage is a temporary storage location in Snowflake where data files are uploaded before being loaded into tables. You can create a stage using:
```sql
CREATE OR REPLACE STAGE csv_stage;
```
Then, use the Snowflake UI or a compatible client tool to upload your CSV file to this stage.

Once the file is in a Snowflake stage, load it into your table using the `COPY INTO` command. Ensure the column mapping is accurate and adjust for any special characters or delimiters if necessary:
```sql
COPY INTO cms_data.collection
FROM @csv_stage/your_file.csv
FILE_FORMAT = (TYPE = 'CSV' FIELD_OPTIONALLY_ENCLOSED_BY = '"');
```

After loading the data, perform a series of checks to ensure the data has been accurately transferred. Use SQL queries to compare row counts, inspect data integrity, and validate that no transformations have altered the data unexpectedly:
```sql
SELECT * FROM cms_data.collection LIMIT 10;
SELECT COUNT(*) FROM cms_data.collection;
```

By following these steps, you can manually move data from Webflow to Snowflake without the use of third-party connectors or integrations.